3-Axis Digital Angular Rate
Gyroscope
FXAS21002C is a small, low-power, yaw, pitch, and roll angular
rate gyroscope with 16 bit ADC resolution. The full-scale range is
adjustable from ±250°/s to ±2000°/s. It features both I2C and SPI
interfaces.
FXAS21002C is capable of measuring angular rates up to
±2000°/s, with output data rates (ODR) from 12.5 to 800 Hz. An
integrated Low-Pass Filter (LPF) allows the host application to
limit the digital signal bandwidth. The device may be configured
to generate an interrupt when a user-programmable angular rate
threshold is crossed on any one of the enabled axes.
FXAS21002C is available in a plastic, 24-lead QFN package; the
device is guaranteed to operate over the extended temperature
range of –40 °C to +85 °C.
Features
Supply voltage (VDD) from 1.95 V to 3.6 V
Interface Supply voltage (VDDIO) from 1.62 V to VDD + 0.3 V
16-bit digital output resolution
±250/500/1000/2000°/s configurable full-scale dynamic
ranges
Full-Scale Range boost function enables FSR's up to
±4000 dps
Angular rate sensitivity of 0.0625°/s in ±2000°/s FSR mode
Noise spectral density of 25 mdps/√Hz at 64 Hz bandwidth
(200 Hz ODR)
Current consumption in Active mode is 2.7 mA
Fast transition from Standby to Active mode (60 ms)
Supported digital interfaces include:
I2C Standard and Fast Mode (100/400 kHz)
SPI Interface (3- and 4-wire modes, up to 2 MHz)
FIFO buffer is 192 bytes (32 X/Y/Z samples) with stop and circular operating modes
Output Data Rates (ODR) from 12.5 to 800 Hz; programmable low-pass filter to further limit digital output
data bandwidth
Low power standby mode
Power mode transition control via external pin for accelerometer-based power management (motion
interrupt)
Rate Threshold interrupt function
Integrated self-test function
8-bit temperature sensor
FXAS21002C
24 QFN
4 mm x 4 mm x 1 mm
Case 2209-01
Top View
1
2
3
4
5
6
7
8 9
10
11
12
14
20
21
24
13
15
16
17
18
19
22
23
SA0 /
VREGD
SPI_CS_B
RSVD_GND
RSVD_GND
GND2
RST_B
INT1
SCL / SCLK
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
I2C_B / SPI
GND1 GND4
GND3
VDD
SDA / MOSI
/ SPI_DATA
MISO
INT2 /
PWR_CTRL
RSVD_GND
RSVD_GND
VDDIO
Pin Connections
Freescale Semiconductor, Inc. FXAS21002C
Data Sheet: Technical Data Rev. 2.1, 5/2015
© 2014-2015 Freescale Semiconductor, Inc. All rights reserved.
Typical Applications
Industrial and consumer grade robots, UAVs, and RC vehicles
Game controller
Gyro-stabilized electronic compass
Orientation determination
Gesture-based user interfaces and Human Machine Interface (HMI)
Indoor navigation
Mobile phones and tablets
Virtual and augmented reality devices (including glasses)
Ordering Information
Part Number Temperature Range Package Description Shipping
FXAS21002CQR1 –40 °C to +85 °C QFN Tape and reel (1 k)
Related Documentation
The FXAS21002C device features and operations are described in a variety of reference manuals, user guides,
and application notes. To find the most-current versions of these documents, go to freescale.com/
FXAS21002C, and then click on the Documentation tab.
2
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table of Contents
1 General Description.............................................................. 4
1.1 Block Diagram............................................................. 4
1.2 Pinout...........................................................................4
1.3 System Connections....................................................5
1.3.1 Typical Application Circuit—I2C Mode.............5
1.3.2 Typical Application Circuit—SPI Mode............ 6
1.4 Sensitive Axes Orientations and Polarities..................7
2 Mechanical and Electrical Specifications.............................. 8
2.1 Absolute Maximum Ratings.........................................8
2.2 Operating Conditions...................................................9
2.3 Mechanical Characteristics..........................................9
2.4 Electrical Characteristics............................................. 10
2.5 Temperature Sensor Characteristics...........................11
3 Digital Interfaces................................................................... 12
3.1 I²C Interface.................................................................12
3.1.1 I²C Operation................................................... 14
3.1.2 I²C Read Operations........................................15
3.1.3 I²C Write Operations........................................ 15
3.2 SPI Interface................................................................17
3.2.1 General SPI Operation.................................... 17
3.2.2 SPI Write Operations with 3- and 4-Wire
Modes.............................................................. 18
3.2.3 SPI Read Operations with 4-Wire Mode..........20
3.2.4 SPI Read Operations with 3-Wire Mode..........21
3.2.5 SPI Timing Specifications (4-wire mode).........21
3.2.6 SPI Timing Specifications (3-wire mode).........23
4 Modes of Operation...............................................................24
5 Functionality..........................................................................26
5.1 FIFO Data Buffer......................................................... 27
5.2 Rate Threshold Detection Function............................. 28
6 Register Descriptions............................................................30
6.1 0x00: STATUS.............................................................30
6.2 0x01–0x06: OUT_X_MSB, OUT_X_LSB,
OUT_Y_MSB, OUT_Y_LSB, OUT_Z_MSB,
OUT_Z_LSB................................................................ 31
6.3 0x07: DR_STATUS......................................................33
6.4 0x08: F_STATUS.........................................................35
6.5 0x09: F_SETUP...........................................................35
6.6 0x0A: F_EVENT.......................................................... 36
6.7 0x0B: INT_SOURCE_FLAG........................................37
6.8 0x0C: WHO_AM_I....................................................... 38
6.9 0x0D: CTRL_REG0..................................................... 38
6.10 0x0E: RT_CFG............................................................ 40
6.11 0x0F: RT_SRC............................................................ 41
6.12 0x10: RT_THS.............................................................43
6.13 0x11: RT_COUNT....................................................... 44
6.14 0x12: TEMP.................................................................44
6.15 0x13: CTRL_REG1......................................................45
6.16 0x14: CTRL_REG2......................................................47
6.17 0x15:CTRL_REG3.......................................................48
7 Printed Circuit Board Layout and Device Mounting.............. 50
7.1 Printed Circuit Board Layout........................................50
7.2 Overview of Soldering Considerations.........................51
7.3 Halogen Content..........................................................52
8 Package Information............................................................. 52
8.1 Product Identification Markings....................................52
8.2 Tape and Reel Information.......................................... 52
8.3 Package Description....................................................53
9 Revision History.................................................................... 55
3
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
1 General Description
1.1 Block Diagram
SCL/SCLK SDA/MOSI/
SPI_DATA
SA0/MISO
SPI/I2C_B
I2C/SPI Interface
C2V ADC-16
Z Vibrating
Mass
Gain
LPF
Z+
Z-
AAF
Charge
Pump Drive Z Programmable
32 Sample
FIFO
Buffer
Configuration
and Control
Registers
Digital I/O
NVM,
Trim Logic
Oscillators,
Clock
Generator
Voltage References
and Regulators
RST_B
VDDIO GND VDD
Drive X/Y
Angular Rate
Demod
MUX
Fd
X/Y Vibrating
Mass
X+ Y+
X- Y-
x,y,z
MUX
INT2/
PWR_CTRL
INT1
Digital
Signal
Processing
Self-Test
Temperature
Sensor
SPI_CS_B
Figure 1. Block Diagram
1.2 Pinout
1
2
3
4
5
6
7
8 9
10
11
12
14
20
21
24
13
15
16
17
18
19
22
23
SA0 /
VREGD
SPI_CS_B
RSVD_GND
RSVD_GND
GND2
RST_B
INT1
SCL / SCLK
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
I2C_B / SPI
GND1 GND4
GND3
VDD
SDA / MOSI
/ SPI_DATA
MISO
INT2 /
PWR_CTRL
RSVD_GND
RSVD_GND
VDDIO
Figure 2. Device pinout (top view)
General Description
4
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 1. Pin functions
Pin Name Function
1 GND1 Ground
2 INT2 / PWR_CTRL1Interrupt Output 2 / Power state transition control input
3 INT1 Interrupt Output 1
4 RST_B Reset input, active low. Connect this pin to VDDIO if unused.
5 GND2 Ground
6 RSVD_GND Reserved - Must be tied to ground
7 RSVD_GND Reserved - Must be tied to ground
8 I2C_B / SPI Digital interface selection pin. This pin must be tied high to select SPI interface
mode, or low to select I2C interface mode.
9 RSVD_GND Reserved pin—must be tied to ground
10 RSVD_GND Reserved pin—must be tied to ground
11 SCL/SCLK I2C / SPI clock
12 SDA / MOSI / SPI_Data I2C data / SPI 4-wire Master Out Slave In / SPI 3-wire data In/Out2
13 SA0/MISO I2C address bit0 / SPI 4-wire Master In Slave Out
14 GND3 Ground
15 VDD Supply voltage
16 VREGD Digital regulator output. Connect a 0.1 μF capacitor between this pin and ground
17 SPI_CS_B SPI chip select input, active low. This pin must be held logic high when operating
in I2C interface mode (I2C_B/SPI set to ground) to ensure correct operation.
18 VDDIO Interface supply voltage
19 GND4 Ground
20 RSVD_GND Reserved - Must be tied to ground
21 RSVD_GND Reserved - Must be tied to ground
22 RSVD_GND Reserved - Must be tied to ground
23 RSVD_GND Reserved - Must be tied to ground
24 RSVD_GND Reserved - Must be tied to ground
1. INT2/PWR_CTRL becomes a high-impedance input with weak internal pull-up resistor when
CTRLREG3[EXTCTRLEN] = 1; the pull-up resistor is referenced to VDDIO.
2. MOSI becomes a bidirectional data pin when FXAS21002C is operated in 3-wire SPI mode with
CTRL_REG0[SPIW]=1.
1.3 System Connections
The FXAS21002C offers the choice of interfacing with a host processor through
either I2C or SPI interfaces. Figure 3 and Figure 4 show the recommended circuit
connections for implementing both interface options.
General Description
5
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
1.3.1 Typical Application Circuit—I2C Mode
1
2
3
4
5
6
7
14
13
15
16
17
18
19
VDDIO
(1.62 to VDD + 0.3 V)
SAO
0.1 μF
0.1 μF
GND1
INT2 / PWR_CTRL
INT1
RST_B
GND2
GND4
VDDIO
SPI_CS_B
VREGD
VDD
GND3
SAO/MISO
SDA
VDDIO
4.7 kΩ
SCL
VDDIO
INT2 / PWR_CTRL
INT1
RSVD_GND
RSVD_GND
4.7 kΩ
VDD (1.95 to 3.6 V)
100 nF
8 9
10
11
12
20
21
24
22
23
SCL/SCLK
SDA/MOSI
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
I2C_B / SPI
47 kΩ
1.0 μF
(optional)
VDDIO
RST_B
Note: Connect RST_B pin to VDDIO
if unused in the application. A pull-up
resistor may be also used if desired.
Note: The logic level on SA0 sets the
7-bit I2C slave address as follows:
SA0 = GND -> 0x20
SA0 = VDDIO -> 0x21
RSVD_GND
RSVD_GND
Figure 3. I2C mode electrical connections
General Description
6
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
1.3.2 Typical Application Circuit—SPI Mode
1
2
3
4
5
6
7
8 9
10
11
12
14
20
21
24
13
15
16
17
18
19
22
23
VDDIO
(1.62 to VDD + 0.3 V)
0.1 μF
0.1 μF
100 nF
Note:
MOSI becomes a bidirectional data pin when
FXAS21002 is operated in 3-wire SPI mode
with CTRL_REG0[SPIW] = 1.
MOSI
MISO
SCLK
Host SPI
Chip Select
SCL/SCLK
SDA/MOSI
RSVD_GND
GND1
INT2 / PWR_CTRL
INT1
RST_B
GND2
GND4
VDDIO
SPI_CS_B
VREGD
GND3
VDD
SAO/MISO
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
RSVD_GND
I2C_B / SPI
INT1
VDDIO
1.0 μF
INT2 /
PWR_CTRL
VDD
(1.95 to 3.6 V)
(Optional)
VDDIO
RST_B
Note: Connect RST_B pin to VDDIO
if unused in the application. A pull-up
resistor may also be used if desired.
47 kΩ
RSVD_GND
RSVD_GND
Figure 4. SPI mode electrical connections
1.4 Sensitive Axes Orientations and Polarities
Z
Y
X
FXAS21002
Figure 5. Reference frame for rotational measurement
General Description
7
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
2 Mechanical and Electrical Specifications
2.1 Absolute Maximum Ratings
Absolute maximum ratings are the limits the device can be exposed to without
permanently damaging it. Absolute maximum ratings are stress ratings only; functional
operation at these ratings is not guaranteed. Exposure to absolute maximum ratings
conditions for extended periods may affect device reliability.
This device contains circuitry to protect against damage due to high static voltage or
electrical fields. It is advised, however, that normal precautions be taken to avoid
application of any voltages higher than maximum-rated voltages to this high-impedance
circuit. Reliability of operation is enhanced if unused inputs are tied to an appropriate
logic voltage level (for instance, either GND or VDD).
Table 2. Absolute maximum ratings
Rating Symbol Min Max Unit
Supply voltage VDD –0.3 3.6 V
Interface supply voltage VDDIO –0.3 3.6 V
Input voltage on any control pin (SA0, SCL, SDA, RST_B, PWR_CTRL) VIN –0.3 VDDIO +0.3 V
Maximum Acceleration (all axes, 100 μs) gmax 5000 g
Operating temperature TOP –40 +85 °C
Storage temperature TSTG –40 +125 °C
Table 3. ESD and latch-up protection characteristics
Rating Symbol Value Unit
Human body model (HBM) VHBM ±2000 V
Machine model (MM) VMM ±200 V
Charge device model (CDM) VCDM ±500 V
Latch-up current at T = 85 °C ILU ±100 mA
Caution
This device is sensitive to mechanical shock, improper handling can cause permanent damage to the part.
Mechanical and Electrical Specifications
8
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Caution
This is an ESD sensitive device, improper handling can cause permanent damage to the part.
2.2 Operating Conditions
Table 4. Nominal operating conditions
Rating Symbol Min Typ Max Unit
Supply voltage VDD 1.95 3.6 V
Interface supply voltage VDDIO 1.62 VDD + 0.3 V
Digital high level input voltage: SCL/SCLK,
SDA/MOSI/SPI_DATA, SA0/MISO, SPI/
I2C_B, RST_B, INT2/PWR_CTRL,
SPI_CS_B pins
VIH 0.7 * VDDIO V
Digital low level input voltage: SCL/SCLK,
SDA/MOSI/SPI_DATA, SA0/MISO, SPI/
I2C_B, RST_B, INT2/PWR_CTRL,
SPI_CS_B pins
VIL 0.3 * VDDIO V
Operating temperature Top –40 +25 +85 °C
2.3 Mechanical Characteristics
Table 5. Mechanical characteristics
Parameter Symbol Test Conditions Min Typ Max Unit
ADC Resolution n 16 bits
Full-scale range FSR
CTRL_REG0[FS] = 00
CTRL_REG0[FS] = 01
CTRL_REG0[FS] = 10
CTRL_REG0[FS] = 11
±2000
±1000
±500
±250
dps
Sensitivity So
CTRL_REG0[FS] = 00
CTRL_REG0[FS] = 01
CTRL_REG0[FS] = 10
CTRL_REG0[FS] = 11
62.5
31.25
15.625
7.8125
mdps/LSB
Sensitivity Temperature Coefficient εT–40 to +85 °C XY: ±0.08 %/°C
Z: ±0.01
Zero-rate Offset DOCTRL_REG0[FS] = 00 ±25 LSB
Zero-rate Offset, Post-Board Mount1DO-PBM CTRL_REG0[FS] = 00 ±50 LSB
Table continues on the next page...
Mechanical and Electrical Specifications
9
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 5. Mechanical characteristics (continued)
Parameter Symbol Test Conditions Min Typ Max Unit
Zero Rate Bias Temperature
Coefficient DT–40 to +85 °C XY: ±0.02 dps/°C
Z: ±0.01
Cross axis sensitivity CAS max(SXY, SXZ, SYX, SYZ,
SZX, SZY) ±1.5 %
Integral nonlinearity
(deviation from linear response) INL CTRL_REG0[FS] = 00 ±0.5 %FSR
Self-test output change2STOC CTRL_REG0[FS] = 00 7000 16000 25000 LSB
Maximum output data rate ODRMAX 800 Hz
Noise density ND
ODR = 200 Hz,
CTRL_REG0[FS] = 00,
CTRL_REG0[BW] = 00
0.025 dps/√Hz
Test conditions (unless otherwise noted):
VDD = 2.5 V
VDDIO = 1.8 V
T = 25 °C
1. Post Board Mount Offset Specifications are based on an eight-layer PCB.
2. The Self-Test function can be used to verify the correct functioning of the ASIC measurement chain and gyro drive
circuitry. The Self-Test function will only produce a meaningful result when the device is maintained stationary during the
test. The Self-Test output value will be either positive or negative due to factory trimming, therefore, the absolute value
of the Self-Test result should be used.
2.4 Electrical Characteristics
Table 6. Electrical characteristics
Parameter Symbol Test conditions Min Typ Max Unit
Supply voltage VDD 1.95 2.5 3.6 V
Interface supply VDDIO 1.62 VDD+0.3 V
Current consumption in Active
mode IddAct Active mode 2.7 mA
Current consumption in Ready
mode IddRdy Ready mode 1.6 mA
Supply current drain in
Standby mode IddStby Standby mode 2.8 µA
Supply current in Standby
mode over temperature IDDSTBY-OT –40 ≤ T ≤ 85 °C 7.5 µA
Digital high level input voltage
SCL/SCLK, SDA/MOSI/
SPI_DATA, SA0/MISO, SPI/
I2C_B, RST_B, INT2/
PWR_CTRL, SPI_CS_B
VIH 0.7 * VDDIO V
Table continues on the next page...
Mechanical and Electrical Specifications
10
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 6. Electrical characteristics (continued)
Parameter Symbol Test conditions Min Typ Max Unit
Digital low level input voltage
SCL/SCLK, SDA/MOSI/
SPI_DATA, SA0/MISO, SPI/
I2C_B, RST_B, INT2/
PWR_CTRL, SPI_CS_B
VIL 0.3 * VDDIO V
High-level output voltage
INT1, INT2/PWR_CTRL,
SDA/MOSI/SPI_DATA, SA0/
MISO
VOH IO = 1 mA 0.9 * VDDIO V
Low-level output voltage INT1,
INT2/PWR_CTRL, SDA/
MOSI/SPI_DATA, SA0/MISO
VOL IO = 1 mA 0.1 * VDDIO V
Low-level output voltage SDA VOLSDA1 IO = 3 mA, VDDIO ≥ 2V 0.4 * VDDIO V
VOLSDA2 IO = 3 mA, VDDIO < 2V 0.2 * VDDIO
Output Data Rate frequency
tolerance ODRTOL ±2.5 % ODR
Output Signal bandwidth BW 4 < ODR/2 256 Hz
Standby to Active mode
transition time TStdy-Act 1/ODR + 60 ms
Ready to Active mode
transition time TRdy-Act 1/ODR + 5 ms
Test conditions (unless otherwise noted):
VDD = 2.5 V
VDDIO = 1.8 V
T = 25°C
2.5 Temperature Sensor Characteristics
Table 7. Temperature sensor characteristics
Characteristic Symbol Condition(s) Min Typ Max Unit
Full-scale range TFSR –40 +85 °C
Operating temperature TOP –40 +25 +85 °C
Sensitivity TSENS 1 °C/LSB
Test conditions (unless otherwise noted):
VDD = 2.5 V
VDDIO = 1.8 V
Mechanical and Electrical Specifications
11
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
3 Digital Interfaces
The registers embedded inside the device are accessed through either an I2C or an SPI
serial interface. To enable either interface, the VDDIO line must be connected to the
interface supply voltage. If VDD is not present and VDDIO is present, FXAS21002C is in
shutdown mode and communications on the interface are ignored. If VDDIO is
maintained, VDD can be powered off and the communications pins will be in a high
impedance state. This will allow communications to continue on the bus with other
devices.
Table 8. Serial interface pin descriptions
Pin name Pin description
VDDIO Digital interface power
SPI_CS_B SPI chip select
SCL/SCLK I2C/SPI serial clock
SDA/MOSI/SPI Data I2C serial data/SPI master serial data out slave serial data in /SPI 3-wire data input/output
SA0/MISO I2C least significant bit of the device address/SPI master serial data in slave serial data out
I2C_B/SPI Digital interface mode selection pin
3.1 I²C Interface
To use the I2C interface, the I2C_B/SPI (pin 8) pin must be connected to GND
(logic low) and the SPI_CS_B (pin 17) must be made logic high (by providing it a
voltage equal to VDDIO). FXAS21002C's I2C interface is compliant with I2C interface
specification for Standard and Fast modes as outlined in the I2C-bus specification and
user manual - Rev 4, published by NXP Semiconductors. The 7-bit slave addresses that
may be assigned to the device are 0x20 (with SA0 = 0) and 0x21 (with SA0 = 1). When
I2C_B/SPI is held low, the SA0/MISO pin is used to define the LSB of this I2C address.
This part does not implement clock stretching. See Table 9 for the I2C slave addresses.
Table 9. I2C Slave Addresses
Command Device Address Bit[0] (SA0
pin state)
Slave Address
Bits[6:0]
R/W Bit Slave Address Byte Transmitted
by Master
Read 0 0x20 1 0x41
Write 0 0x20 0 0x40
Read 1 0x21 1 0x43
Write 1 0x21 0 0x42
Digital Interfaces
12
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
The key bus timing constraints are shown in Table 10. The I2C timing diagram is
shown in Figure 6.
Table 10. Slave timing values
Parameter Symbol I2C Standard Mode1, 2I2C Fast Mode1, 2Unit
Min Max Min Max
SCL clock frequency fSCL 0 100 0 400 kHz
Bus free time between STOP and
START conditions tBUF 4.7 1.3 µs
Hold time (repeated) START condition tHD;STA 4.0 0.6 µs
Set-up time for a repeated START
condition tSU;STA 4.7 0.6 µs
Set-up time for a STOP condition tSU;STO 4.0 0.6 µs
SDA valid time2tVD;DAT 3.453 0.93µs
SDA valid acknowledge time4tVD;ACK 3.453 0.93µs
SDA setup time tSU;DAT 250 1005 ns
SCL clock low time tLOW 4.7 1.3 µs
SCL clock high time tHIGH 4.0 0.6 µs
SDA and SCL rise time tr 1000 20 300 ns
SDA and SCL fall time6tf 300 20*(VDDIO/5.5 V) 300 ns
Capacitive load for each bus line7Cb 400 400 pF
Pulse width of spikes on SDA and SCL
that must be suppressed by the internal
input filter
tSP 0 50 0 50 ns
1. All values refer to VIH (min) and VIL (max) levels.
2. tVD;DAT refers to the time for data signal from SCL LOW to SDA output (HIGH or LOW, depending on which one is
worse).
3. The maximum tHD;DAT could be 3.45 µs and 0.9 µs for Standard mode and Fast mode, but must be less than the
maximum of tVD;DAT or tVD;ACK by a transition time.
4. tVD;ACK = time for acknowledgement signal from SCL LOW to SDA output (HIGH or LOW, depending on which one is
worse).
5. A Fast-mode I2C device can be used in a Standard-mode I2C system, but the requirement tSU;DAT 250 ns must then
be met. Also, the acknowledge timing must meet this set-up time.
6. The maximum tf for the SDA and SCL bus lines is specified at 300 ns. The maximum fall time for the SDA output
stage tf is specified at 250 ns. This allows series protection resistors to be connected between the SDA and the SCL
pins and the SDA/SCL bus lines without exceeding the maximum specified tf.
7. Cb is the total capacitance of one bus line in pF; the maximum bus capacitance allowable may vary from this value
depending on the application operating voltage and frequency.
Digital Interfaces
13
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
70%
30%
70%
30%
70%
30%
70%
30%
70%
30%
70%
30%
1 / fSCL tLOW
tSU:DAT
1st clock cycle
tVD:DAT
9th clock
tHIGH
SDA
SCL
SDA
SCL
tSU:STAtHD:STAtSP
tHD :DAT
tSU:STO
tVD:ACK
70%
30%
9th clock
tr
tr
tr
SP
tSET
S
tBUF
tr
Sr
Figure 6. I2C timing diagram
3.1.1 I²C Operation
There are two signals associated with the I2C bus: the serial clock line (SCL) and the
serial data line (SDA). The SDA is a bidirectional line used for sending and receiving
the data to and from the interface. External pull-up resistors connected to VDDIO are
required for SDA and SCL. When the bus is free, the lines are high.
The maximum practical operating frequency for I2C in a given system implementation
depends on several factors including the pull-up resistor values, and the total bus
capacitance (trace + parasitic device capacitances).
A transaction on the bus is started through a start condition (ST) signal, which is
defined as a HIGH-to-LOW transition on the data line while the SCL line is held HIGH.
After the ST signal has been transmitted by the master, the bus is considered busy. The
next byte of data transmitted contains the slave address in the first seven bits, and the
eighth bit, the read/write bit, indicates whether the master is receiving data from the
slave or transmitting data to the slave. When an address is sent, each device in the
system compares the first seven bits after the ST condition with its own address. If they
match, the device considers itself addressed by the master. The ninth clock pulse,
following the slave address byte (and each subsequent byte) is the acknowledge (ACK).
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
The transmitter must release the SDA line during the ACK period. The receiver must
then pull the data line low so that it remains consistently low during the high period of
the acknowledge clock period. The number of bytes per transfer is unlimited. If a
receiver can't receive another complete byte of data until it has performed some other
function, it can hold the clock line, SCL, low to force the transmitter into a wait state.
Data transfer only continues when the receiver is ready for another byte and releases
the data line. This delay action is called clock stretching. Not all receiver devices
support clock stretching. Not all master devices recognize clock stretching.
A LOW-to-HIGH transition on the SDA line while SCL is high is defined as a stop
condition (SP) signal. A write or burst write is always terminated by the master
issuing the SP signal. A master should properly terminate a read by not
acknowledging a byte at the appropriate time in the protocol. A master may also issue
a repeated start signal (SR) during a transfer.
3.1.2 I²C Read Operations
3.1.2.1 Single-Byte Read
The master (or MCU) transmits an ST to the FXAS21002C, followed by the slave
address, with the R/W bit set to “0” for a write, and the FXAS21002C sends an
acknowledgement. Then, the MCU transmits the address of the register to read and the
FXAS21002C sends an acknowledgement. The MCU transmits an SR, followed by
the byte containing the slave address and the R/W bit set to “1” for a read from the
previously selected register. The FXAS21002C then acknowledges and transmits the
data from the requested register. The master transfers a NACK followed by an SP,
signaling an end of transmission.
3.1.2.2 Multiple-Byte Read
When performing a multiple-byte or burst read, the FXAS21002C increments the
register address read pointer after a read command is received. Therefore, after
following the steps of a single-byte read, multiple bytes of data can be read from
sequential registers after each FXAS21002C ACK is received. This continues until the
master transfers a NACK followed by an SP, signaling an end of transmission.
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
3.1.3 I²C Write Operations
3.1.3.1 Single-Byte Write
To start a write command, the master transmits an ST to the FXAS21002C, followed by
the slave address with the R/W bit set to “0” for a write, and the FXAS21002C sends an
ACK. Then, the master transmits the address of the register to write to, and the
FXAS21002C sends an ACK. Then, the master transmits the 8-bit data to write to the
designated register and the FXAS21002C sends an ACK that it has received the data.
Since this transmission is complete, the master transmits an SP to end the data transfer.
The data sent to the FXAS21002C is now stored in the appropriate register.
3.1.3.2 Multiple-Byte Write
The FXAS21002C automatically increments the register address write pointer after a
write command is received. Therefore, after following the steps of a single-byte write,
multiple bytes of data can be written to sequential registers after each FXAS21002C
ACK is received.
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
3.1.3.3 I²C Data Sequence Diagrams
<Single Byte Read>
<Multiple Byte Write>
ST Device Address[6:0]
W
SP
Master
Slave
<Single Byte Write>
<Multiple Byte Read>
Master
Slave
Master
Slave
Register Address[7:0]
Legend
ST: Start Condition SR: Repeated Start Condition
SP: Stop Condition NACK: No Acknowledge W: Write = 0
ACK: Acknowledge
ACKACK
ACK
ACK
ST Device Address[6:0]
W
SP
Register Address[7:0]
ACK
ACK
ACK
SP
Data[7:0]
ACKACK
Data[7:0] Data[7:0]
NACK
ST Device Address[6:0]
W
Register Address[7:0]
ACK
ACK
ACK
SR Device Address[6:0] R
Data[7:0]
ACK
continued
<Multiple Byte Read>
SP
ACKACK NACK
ST Device Address[6:0]
W
Register Address[7:0]
ACK
ACK
ACK
SR Device Address[6:0] R
continued
ACK
ST Device Address[6:0]
W
Register Address[7:0]
ACK
ACK
SR Device Address[6:0] R
ACK
SP
NACK
Data[7:0]
Data[7:0]
Data[7:0] Data[7:0] Data[7:0]
Data[7:0]
Data[7:0] Data[7:0]
Master
Slave
Master
Slave
Master
Slave
Master
Slave
Figure 7. I²C data sequence diagram
3.2 SPI Interface
The SPI interface is a classical Master/Slave serial port. FXAS21002C is always
considered to be the slave device and thus never initiates a communication with the
host processor.
The SPI interface of FXAS21002C is compatible with SPI interface mode 00,
corresponding to CPOL = 0 and CPHA = 0.
For CPOL = 0, the idle value of the clock is zero, and the active value of the clock is
1. For CPHA = 0, data is captured on the clock's rising edge (low to high transition)
and data is propagated on the clock’s falling edge (high to low transition).
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
3.2.1 General SPI Operation
The SPI_CS_B pin is driven low at the start of a transaction, held low for the duration
of the transfer, and then driven high again after the transaction is completed. During a
transaction, the master toggles the clock (SCLK). The SCLK polarity is defined as
having an idle value that is low, and an active phase that is high (CPOL = 0). Serial
input and output data is captured on the clock's rising edge and propagated on the
falling edge (CPHA = 0). Single byte read and single byte write operations are
completed in 16 SCLK cycles; multiple byte reads and writes are completed in
additional multiples of 8 SCLK cycles. The first SCLK cycle latches the most
significant bit on MOSI to select whether the desired operation is a read (R/W = 1) or a
write (R/W = 0). The following seven SCLK cycles are used to latch the slave register
read or write address.
NOTE
4-wire SPI interface mode is the default out of POR or after a
hard/soft reset. The 3-wire interface mode may be selected by
setting CTRL_REG0[SPIW] = 1.
3.2.2 SPI Write Operations with 3- and 4-Wire Modes
A write operation is initiated by transmitting a 0 for the R/W bit. Then, the 7-bit register
write address, A[6:0], is transmitted in MSb first order. The data byte to be written is
then transferred during the second 8 SCLK cycle period (again, with MSb first). Figure
8 and Figure 9 shows the bus protocol for a single byte register write operation in either
3- or 4-wire SPI modes.
Figure 8. SPI single byte write protocol diagram (4-wire mode), R/W = 0
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Figure 9. SPI single byte write protocol diagram (3-wire mode), R/W = 0
Multiple-byte write operations are performed similarly to the single-byte write
sequence, but with additional data bytes transferred over every 8 SCLK cycle period.
The register write address is internally auto-incremented by FXAS21002C so that
every eighth clock edge will latch the address for the next register write address.
When the desired number of bytes has been written, the rising edge on the SPI_CS_B
pin terminates the transaction. Figure 10 and Figure 11 show the bus protocol for
multiple byte register write operation in either 3- or 4-wire SPI modes.
MISO
MOSI
SCLK
SPI_CS_B
12 3 4 5 6 7 8 9 10 11 12 13 14 15 16
R/W A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
17 18 19 20 21 22 23 24
D7 D6 D5 D4 D3 D2 D1 D0
Figure 10. SPI multiple byte write protocol diagram (4-wire mode), R/W = 0
MISO
MOSI
SCLK
SPI_CS_B
12 3 4 5 6 7 8 9 10 11 12 13 14 15 16
R/W A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
17 18 19 20 21 22 23 24
D7 D6 D5 D4 D3 D2 D1 D0
High-Impedance
Figure 11. SPI multiple byte write protocol diagram (3-wire mode), R/W = 0
Digital Interfaces
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
3.2.3 SPI Read Operations with 4-Wire Mode
NOTE
This description pertains only to the default SPI 4-wire
interface mode (with CTRL_REG0[SPIW] = 0). This mode is
the default out of POR, or after a hard/soft reset.
A register read operation is initiated by transmitting a 1 for the R/W bit. Then, the 7-bit
register read address, A[6:0] is encoded in the first byte. The data is read from the
MISO pin (MSB first). Figure 12 shows the bus protocol for a single byte read
operation.
Figure 12. SPI single byte read protocol diagram (4-wire mode), R/W = 1
Multiple-byte read operations are performed similarly to single-byte reads; additional
bytes are read in multiples of eight SCLK cycles. The register read address is auto-
incremented by FXAS21002C so that every eighth clock edge will latch the address of
the next register read address. When the desired number of bytes has been read, the
rising edge on the SPI_CS_B terminates the transaction.
MISO
MOSI
SCLK
SPI_CS_B
12 3 4 5 6 7 8 9 10 11 12 13 14 15 16
R/W A6 A5 A4 A3 A2 A1 A0
17 18 19 20 21 22 23 24
D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
Figure 13. SPI multiple byte read protocol diagram (4-wire mode), R/W = 1
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
3.2.4 SPI Read Operations with 3-Wire Mode
NOTE
This description pertains only to the 3-wire SPI interface
mode (with CTRL_REG0[SPIW] = 1). This interface mode
is not the default and must be selected after a POR, or hard/
soft reset.
FXAS21002C can be configured to operate in 3-wire SPI mode. In this mode the
MISO pin is left unconnected or high-z, and the MOSI pin becomes a bi-directional
input/output pin (SPI_DATA). 3-wire mode is selected by setting the SPIW bit in
CTRL_REG0. Read operations in 3-wire mode are the same as in 4-wire mode
except that at the end of address cycle, the MOSI (SPI_DATA) pin automatically
switches from an input to an output.
Figure 14. SPI single byte read protocol diagram (3-wire mode)
MISO
MOSI
SCLK
SPI_CS_B
12 3 4 5 6 7 8 9 10 11 12 13 14 15 16
R/W A6 A5 A4 A3 A2 A1 A0
17 18 19 20 21 22 23 24
D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
High-Impedance
Figure 15. SPI multiple byte read protocol diagram (3-wire mode)
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
3.2.5 SPI Timing Specifications (4-wire mode)
Table 11 and Figure 16 specify and illustrate the minimum and maximum timing
parameter values for correct SPI interface functionality when FXAS21002C is operated
in 4-wire SPI mode. The timing delays given in Table 11 are taken at 70% of the rising
edge and 30% of the falling edge. FXAS21002C only supports SPI mode 00,
corresponding to CPOL = 0, and CPHA = 0. In this mode, the active state of the clock
is high and the idle state is low. Data is latched on the rising edge of the clock and
propagated on the falling edge. Please note that the timing parameters shown in Table
11 are based on simulations performed across process, voltage, and temperature with a
total bus capacitance of 80 pF and a 10 kΩ pull-up resistor to VDDIO on each SPI
interface pin (SCL/SCLK, SDA/MOSI/SPI_DATA, SA0/MISO, and SPI_CS_B).
NOTE
In 4-wire SPI mode the MISO pin is always placed in a high
impedance state when CS_B is not asserted (logic high level).
Table 11. Slave timing values
Label Description Specifications Unit
Min. Max.
fSCLK SCLK frequency 0 2 MHz
tSCLK SCLK Period 500 ns
tSCLKH SCLK high time 210 ns
tSCLKL SCLK low time 210 ns
tSZ Setup time for MISO signal (transition out of
high-z state)
130
tHZ Hold time for MISO signal (transition back to
high-z state)
110
tSCS Setup time for SPI_CS_B signal 250 ns
tHCS Hold time for SPI_CS_B signal 200 ns
tWCS Inactive time for SPI_CS_B signal 110 ns
tSET Data setup time for MOSI signal 20 ns
tHOLD Data hold time for MOSI signal 200 ns
tDDLY Data setup time for MISO signal 210 ns
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
tWCS
tHCS
tSCLKL
tSCLKH
tSCLK
tSCS
tSET
tHOLD tDDLY
SPI_CS_B
SCLK
MOSI
MISO
Figure 16. SPI timing diagram (4-wire mode)
3.2.6 SPI Timing Specifications (3-wire mode)
Table 12 and Figure 17 specify and illustrate the minimum and maximum timing
parameter values for correct SPI interface functionality when FXAS21002C is
operated in 3-wire SPI mode. The timing delays given in Table 12 are taken at 70% of
the rising edge and 30% of the falling edge. FXAS21002C only supports SPI mode
‘00’, corresponding to CPOL = 0, and CPHA = 0. In this mode, the active state of the
clock is high and the idle state is low. Data is latched on the rising edge of the clock
and propagated on the falling edge. Please note that the timing parameters shown in
Table 12 are based on simulations performed across process, voltage, and temperature
with a total bus capacitance of 80pF and a 10 kΩ pull-up resistor to VDDIO on each
SPI interface pin (SCL/SCLK, SDA/MOSI/SPI_DATA, SA0/MISO, and SPI_CS_B).
NOTE
When FXAS21002C is operated in 3-wire SPI mode - by
setting CTRL_REG0[SPIW] = 1 - the SA0/MISO pin is
always placed in a high impedance (high-z) state.
Table 12. Slave timing values
Label Description Specifications Unit
Min. Max.
fSCLK SCLK frequency 0 1.4 MHz
tSCLK SCLK Period 714 ns
tSCLKH SCLK high time 300 ns
Table continues on the next page...
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 12. Slave timing values (continued)
Label Description Specifications Unit
Min. Max.
tSCLKL SCLK low time 300 ns
tHZ Hold time for MISO signal (transition back to
high-z state)
200
tSCS Setup time for SPI_CS_B signal 250 ns
tHCS Hold time for SPI_CS_B signal 200 ns
tWCS Inactive time for SPI_CS_B signal 200 ns
tSET Data setup time for MOSI signal 20 ns
tHOLD Data hold time for MOSI signal 200 ns
tDDLY Data setup time for MISO signal 280 ns
tWCS
tHCS
tSCLKL
tSCLKH
tSCLK
tSCS
tSET
tHOLD
tDDLY
SPI_CS_B
SCLK
MOSI
MISO High-Impedance
Figure 17. SPI timing diagram (3-wire mode)
4 Modes of Operation
The device may be placed into one of three functional modes:
Standby: Some digital blocks are enabled; I2C/SPI communication is possible.
This mode is the minimum power consumption state for the device and is the
default mode entered on POR or hard/soft reset. A transition from Standby mode to
Active mode takes 1/ODR + 60 ms, typical.
Modes of Operation
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Active: All blocks are enabled (digital and analog); the device is actively
measuring the angular rate at the ODR specified in 0x13: CTRL_REG1. This is
the maximum power consumption state of the device.
Ready: This mode is entered by setting CTRL_REG1[Ready] = 1. In this mode,
the drive circuits are running but no measurements are being made. This mode
offers the user the ability to significantly reduce the current draw of the device
while providing a fast transition into Active mode within 1/ODR + 5 ms.
NOTE
When CTRL_REG3[EXTCTRLEN] = 0, the Active mode
is entered/exited using the register interface
(CTRL_REG1[ACTIVE] bit). When
CTRL_REG3[EXTCTRLEN] = 1, the Active mode is
entered/exited via the logic state on the PWR_CTRL input
pin (pin 2).
The functional mode is selected using CTRL_REG1. After a POR (Power on Reset), a
boot sequence is performed by the device and the registers are loaded with their preset
values. After the boot sequence completes, the default operating mode of
FXAS21002C is Standby mode.
POR (VDD > 1.95 V)
CTRL_REG1[ACTIVE] = 1
Functional modes
Start-up sequence
Boot_end = 1
Ready
Standby
Active
Boot
CTRL_REG1[ACTIVE] = 0
and
CTRL_REG1[READY] = 0
CTRL_REG1[ACTIVE] = 0
and
CTRL_REG1[READY] = 1
CTRL_REG1[ACTIVE] = 1
CTRL_REG1[ACTIVE] = 0
and
CTRL_REG1[READY] = 0
CTRL_REG1[ACTIVE] =0
and
CTRL_REG1[READY] = 1
Figure 18. Functional mode transition diagram with CTRL_REG3[EXTCTRLEN] = 0
Modes of Operation
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Freescale Semiconductor, Inc.
POR (VDD > 1.95 V)
PWR_CTRL = HIGH
Functional modes
Start-up sequence
Boot_end = 1
Standby
Boot
PWR_CTRL = Low
and
CTRL_REG1[READY] = 0 PWR_CTRL = Low
and
CTRL_REG1[READY] = 1
Ready
Active
PWR_CTRL = HIGH
PWR_CTRL = Low
and
CTRL_REG1[READY] = 1
PWR_CTRL = Low
and
CTRL_REG1[READY] = 0
Figure 19. Functional mode transition diagram with CTRL_REG3[EXTCTRLEN] = 1
5 Functionality
The FXAS21002C is a low-power, digital-output, 3-axis gyroscope with both I2C and
SPI interfaces. The functionality includes the following:
16-bit output data presented in 2's complement format
Configurable full scale ranges of ±250, ±500, ±1000 and ±2000 dps; optional FSRs
of ±500, ±1000, ±2000 and ±4000 by setting CTRL_REG3[FS_DOUBLE] = 1
Configurable output data rates from 12.5 to 800 Hz
Internal low-pass filter with programmable cut-off frequency to limit the output
data bandwidth
Angular rate sensitivity of 0.0625°/s in ±2000°/s FSR mode
Internal high-pass filter with programmable cut-off frequency
Embedded rate threshold detection function with programmable debounce time
32-sample FIFO configurable in Circular or Stop data collection modes
2 external interrupt pins that are configurable to signal data-ready, Rate Threshold
or FIFO events
Self-test function for indication of device health
Functionality
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Data for each axis must be read from the respective data registers, two bytes at a time;
for example, one byte for most significant byte and one byte for least significant.
Combining these two bytes results in a 16-bit 2's complement signed integer with the
sign bit in bit location #15 and the least significant bit in location 0. See the tables
below:
Bit 15 14 13 12 11 10 9 8
Data bit D15 D14 D13 D12 D11 D10 D9 D8
Sign bit
Bit76543210
Data bit D7 D6 D3 D4 D3 D2 D1 D0
LSB
The conversion from counts to units of dps is done by first adjusting the byte order of
the output data (if needed). On a big-endian processor, no byte order changes are
needed. On a little-endian processor, the byte order (MSB, LSB) must be swapped.
Following this step, the 16-bit value is multiplied by the appropriate sensitivity value
for the selected full scale range. See Table 35 for nominal sensitivity values.
5.1 FIFO Data Buffer
FXAS21002C contains a FIFO data buffer that is 192 bytes (32 X/Y/Z samples) and is
useful for reducing the frequency of transactions on the I2C/SPI bus. The FIFO can
also provide system level power savings by allowing the host processor/MCU to go
into a sleep/low-power mode while the FXAS21002C collects up to 32 samples of 3-
axis angular rate data.
The FIFO is configured to operate in Circular Buffer mode or Stop mode, depending
on the settings made in the 0x09: F_SETUP register. The Circular Buffer mode allows
the FIFO to be filled with a new sample, replacing the oldest sample in the buffer. The
most recent 32 samples will be stored in the buffer. This is useful in situations where
the processor is waiting for a specific interrupt to indicate that the data must be
flushed to analyze the event.
The FXAS21002C FIFO Buffer has a configurable watermark, allowing an interrupt
to be signaled to the processor after a configurable number of samples enter the buffer
(1 to 32).
Functionality
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
5.2 Rate Threshold Detection Function
The embedded rate detection function can be used to detect an angular rate event that
exceeds a programmed threshold on any one of the enabled axes for longer than the
programmed debounce time, triggering an interrupt on one of the INT1/INT2 pins (if
enabled).
Sign
|x|
Data
RT_THS
DBCNTM
RT_COUNT
ELE
>CNT
>RT
RT_Pol
LATCH
LATCH
ELE
Output data rate (Hz) ODR and counter clock period (ms) Event debounce time range (s)
800 1.25 0 – 0.32
400 2.5 0 – 0.64
200 5 0 – 1.28
100 10 0 – 2.56
50 20 0 – 5.12
25 40 0 – 10.24
12.5 80 0 – 20.48
If the debounce counter reaches the value stored in RT_COUNT, the rate threshold
event is detected. The interrupt flag can be either latched or updated in real-time
depending on the state of the ELE bit. The examples illustrated in Figure 20 through
Figure 23 show the use of the rate threshold function with the various settings for the
DBCNTM and ELE control bits:
Functionality
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Data
Counter control
Counter value
RT
RT_COUNT
RT_THS
t
Figure 20. ELE = 0 and DBCNTM = 0
Data
Counter control
Counter value
RT
RT_COUNT
RT_THS
t
Figure 21. ELE = 0 and DBCNTM = 1
Data
Counter control
Counter value
Resetting the flag
RT_COUNT
RT_THS
t
RT
Figure 22. ELE = 1 and DBCNTM = 0
Data
Counter control
Counter value
Resetting the flag
RT_COUNT
RT_THS
t
RT
Figure 23. ELE = 1 and DBCNTM = 1
Functionality
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
6 Register Descriptions
Table 13. Register address map
Name Type Register
address
Auto-increment
address
Default
value
Comment
STATUS R 0x00 0x01 0x00 Alias for DR_STATUS or F_STATUS
OUT_X_MSB R 0x01 0x02 0x001[7:0] are 8 MSBs of 16 bit X-axis data sample
OUT_X_LSB R 0x02 0x03 0x001[7:0] are 8 MSBs of 16 bit X-axis data sample
OUT_Y _MSB R 0x03 0x04 0x001[7:0] are 8 MSBs of 16 bit Y-axis data sample
OUT_Y_LSB R 0x04 0x05 0x001[7:0] are 8 MSBs of 16 bit Y-axis data sample
OUT_Z_MSB R 0x05 0x06 0x001[7:0] are 8 MSBs of 16 bit Z-axis data sample
OUT_Z_LSB R 0x06 0x00/0x01 0x001
[7:0] are 8 MSBs of 16 bit Z-axis data sample;
Auto-increment address depends on the
setting made in CTRL_REG3[WRAPTOONE]
(defaults to 0x00)
DR_STATUS R 0x07 0x08 0x00 Data-ready status information
F_STATUS R 0x08 0x09 0x00 FIFO Status
F_SETUP R/W 0x09 0x0A 0x00 FIFO setup
F_EVENT R 0x0A 0x0B 0x00 FIFO event
INT_SRC_FLAG R 0x0B 0x0C 0x00 Interrupt event source status flags
WHO_AM_I R 0x0C 0x0D 0xD7 Device ID
CTRL_REG0 R/W 0x0D 0x0E 0x00 Control register 0: Full-scale range selection,
high-pass filter setting, SPI mode selection
RT_CFG R/W 0x0E 0x0F 0x00 Rate threshold function configuration
RT_SRC R 0x0F 0x10 0x00 Rate threshold event flags status register
RT_THS R/W 0x10 0x11 0x00 Rate threshold function threshold register
RT_COUNT R/W 0x11 0x12 0x01 Rate threshold function debounce counter
TEMP R 0x12 0x13 0x00 Device temperature in °C
CTRL_REG1 R/W 0x13 0x14 0x00 Control register 1: Operating mode, ODR
selection, self-test and soft reset
CTRL_REG2 R/W 0x14 0x15 0x00 Control register 2: Interrupt configuration
settings
CTRL_REG3 R/W 0x15 0x00 0x00
Control Register 3: Auto-increment address
configuration, external power control, FSR
expansion
RESERVED 0x16 – 0xFF address + 1 Factory reserved register space
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Register Descriptions
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6.1 0x00: STATUS
The STATUS register content depends on the FIFO mode setting. It is a copy of either
0x07: DR_STATUS or 0x08: F_STATUS. This allows for easy reading of the
relevant status register before reading the current sample output data, or the first
sample stored in the FIFO.
6.2 0x01–0x06: OUT_X_MSB, OUT_X_LSB, OUT_Y_MSB,
OUT_Y_LSB, OUT_Z_MSB, OUT_Z_LSB
The X-axis, Y-axis, and Z-axis output rate data are represented in 16-bit, 2's
complement format. The output data registers are arranged in a contiguous big endian
format, with the MSB of each axis’s data located at the lower register address. The
output data registers are either updated at the selected output data rate (with
F_SETUP[F_MODE] equal to 0b00 ), or alternately, point to the head of the FIFO
buffer (with F_SETUP[F_MODE] greater than 0b00 ). When reading a data sample
with F_MODE equal to 0b00, the host must always start by reading the MSB of each
axis first to ensure that the corresponding LSB register is also updated with the current
sample data. When F_MODE is greater than 0b00, the OUT_X_MSB register must be
read out first in order for the other five output data registers (OUT_X_LSB through
OUT_Z_LSB) to be updated with sample data stored at the head of the FIFO. The
FIFO head pointer is only incremented to point to the next stored sample when the
host reads the OUT_Z_MSB register.
NOTE
To avoid the loss of data, the user must burst-read all six
bytes of sample data (three axes) in a single I2C or SPI
transaction.
Table 14. 0x01: OUT_X_MSB
Bit76543210
Read XD[15:8]
Write
Reset100000000
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Register Descriptions
31
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 15. 0x02: OUT_X_LSB
Bit76543210
Read XD[7:0]
Write
Reset10000000
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Table 16. 0x03: OUT_Y_MSB
Bit76543210
Read YD[15:8]
Write
Reset100000000
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Table 17. 0x04: OUT_Y_LSB
Bit76543210
Read YD[7:0]
Write
Reset100000000
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Table 18. 0x05: OUT_Z_MSB
Bit76543210
Read ZD[15:8]
Write
Reset100000000
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Table 19. 0x06: OUT_Z_LSB
Bit76543210
Read ZD[7:0]
Write
Reset100000000
1. As shown on POR. On hard/soft reset, the default value cannot be determined.
Register Descriptions
32
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
NOTE
After this register is read, the next read register by the auto-
increment process is STATUS at 0x00, when
CTRL_REG3[WRAPTOONE] = 0, or OUT_X_MSB when
CTRL_REG3[WRAPTOONE] = 1.
Data output LSB registers only contain valid data after a
read of the corresponding axis MSB data register. When
F_SETUP[F_MODE] > 0b00, a data read operation must
start by reading the OUT_X_MSB register in order for the
contents of the other output data registers to be updated for
the currently indexed buffered sample. With
F_SETUP[F_MODE] > 0b00, the OUT_Z_MSB register
must be read in order to advance the internal buffer read
pointer to index the next sample stored in the FIFO.
6.3 0x07: DR_STATUS
The DR_STATUS register provides the sample data acquisition status and reflects the
real-time updates to the OUT_X, OUT_Y, and OUT_Z registers. The content of this
register is reset upon a transition from Standby to Active or from Ready to Active
modes.
Table 20. DR_STATUS register
Bit76543210
Read ZYXOW ZOW YOW XOW ZYXDR ZDR YDR XDR
Write
Reset00000000
Table 21. DR_STATUS field descriptions
Field Description
7
ZYXOW
X-, Y-, Z-axis data overwrite
Asserted whenever new X-, Y-, and Z-axis data is acquired before completing the retrieval of the
previous set.
Cleared after the high-bytes of the data of all channels (OUT_X_MSB, OUT_Y_MSB,
OUT_Z_MSB) are read.
0: No data overwrite has occurred
1: X, Y, and Z data overwrite occurred before the previous data was read
Table continues on the next page...
Register Descriptions
33
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 21. DR_STATUS field descriptions (continued)
Field Description
6
ZOW
Z-axis data overwrite
Asserted whenever a new Z-axis acquisition is completed before the retrieval of the previous data.
When this occurs, the previous data is overwritten.
Cleared anytime the OUT_Z_MSB (and respectively OUT_Y_MSB, OUT_X_MSB) register is read.
0: No data overwrite has occurred
1: Z-axis data overwrite occurred before the previous data was read
5
YOW
Y-axis data overwrite
Asserted whenever a new Y-axis acquisition is completed before the retrieval of the previous data.
When this occurs, the previous data is overwritten.
Cleared anytime the OUT_Z_MSB (and respectively OUT_Y_MSB, OUT_X_MSB) register is read.
0: No data overwrite has occurred
1: Y-axis data overwrite occurred before the previous data was read
4
XOW
X-axis data overwrite
Asserted whenever a new X-axis acquisition is completed before the retrieval of the previous data.
When this occurs, the previous data is overwritten.
Cleared anytime the OUT_Z_MSB (and respectively OUT_Y_MSB, OUT_X_MSB) register is read.
0: No data overwrite has occurred
1: X-axis data overwrite occurred before the previous data was read
3
ZYXDR
X-, Y-, and Z-axis data available
Signals that a new acquisition for any of the channels is available.
Cleared when the high-bytes of the data of all channels (OUT_X_MSB, OUT_Y_MSB,
OUT_Z_MSB) are read.
0: No new data is ready
1: New data is ready
2
ZDR
Z-axis new data available
Asserted whenever a new Z-axis data acquisition is completed.
Cleared anytime the OUT_Z_MSB register is read.
0: No new Z-axis data is ready
1: New Z-axis data is ready
1
YDR
Y-axis new data available
Asserted whenever a new Y-axis data acquisition is completed.
Cleared anytime the OUT_Y_MSB register is read.
0: No new Y-axis data is ready
1: New Y-axis data is ready
0
XDR
X-axis new data available
Asserted whenever a new X-axis data acquisition is completed.
Cleared anytime the OUT_X_MSB register is read.
0: No new X-axis data is ready
1: New X-axis data is ready
Register Descriptions
34
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
6.4 0x08: F_STATUS
When the FIFO is enabled, the F_STATUS register indicates the current status of the
FIFO. Also, the STATUS register (address 0x00) contains the same content as
F_STATUS to facilitate the emptying of the FIFO by the host processor. The content
of this register is reset upon a transition from Standby to Active or from Ready to
Active modes.
Table 22. F_STATUS register
Bit76543210
Read F_OVF F_WMKF F_CNT[5:0]
Write
Reset00000000
Table 23. F_Status field descriptions
Field Description
7
F_OVF
FIFO overflow flag
A FIFO overflow event, such as when F_CNT = 32 and a new sample arrives, asserts the F_OVF
flag.
Cleared when the FIFO sample count goes below 32.
0: No overflow detected
1: Overflow detected
6
F_WMKF
FIFO watermark flag
A FIFO sample count greater than or equal to the sample count watermark (determined by the
F_WMRK field in register 0x09: F_SETUP) asserts the F_WMKF event flag.
Cleared when FIFO sample count goes below the sample count watermark (set by the value of
F_SETUP[F_WMRK] field).
0: No watermark event detected
1: Watermark event detected
5:0
F_CNT
FIFO sample counter
Indicates the number of samples currently stored in the FIFO.
A count value of 0b000000 indicates that the FIFO is empty.
6.5 0x09: F_SETUP
The F_SETUP register is used to configure the FIFO. The FIFO update rate is set by
the selected system ODR (DR bits in 0x13: CTRL_REG1). The contents should be
modified only when the device is in Standby mode.
Register Descriptions
35
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 24. F_Setup register
Bit76543210
Read F_MODE[1:0] F_WMRK[5:0]
Write
Reset00000000
Table 25. F_SETUP field descriptions
Field Description
7:6
F_MODE
FIFO operating mode selection:
00: FIFO is disabled
01: Circular Buffer mode
1x: Stop mode
Note:
Used to select the FIFO operating mode.
In the Circular Buffer mode, the oldest sample is discarded and replaced by the newest sample when
the buffer is full with F_STATUS[F_CNT] = 32.
In the Stop mode, the FIFO will stop accepting new samples when the buffer is full with
F_STATUS[F_CNT] = 32.
The FIFO operating mode cannot be switched between Circular and Stop modes while the FIFO is
enabled.
To change the FIFO operating mode, the FIFO function must first be disabled by setting F_MODE[1:0] =
00.
The FIFO is cleared whenever the FIFO is disabled.
5:0
F_WMRK
FIFO sample count watermark setting
Used to set the watermark level.
To suppress FIFO watermark event flag generation, F_WMRK[5:0] can be set to 0x00.
Disabling the FIFO clears F_WMKF
A FIFO sample count exceeding the watermark level does not stop the FIFO from accepting new data.
Default value is 0b000000.
6.6 0x0A: F_EVENT
The F_EVENT register is used to monitor the FIFO event status. The content of this
register is reset upon a transition from Standby to Active or from Ready to Active
modes.
Table 26. F_Event register
Bit76543210
Read 0 0 F_EVENT FE_TIME[4:0]
Write
Reset00000000
Register Descriptions
36
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 27. F_EVENT field descriptions
Field Description
5
F_EVENT
FIFO Event
Indicates if either F_OVF or F_WMKF flags are set (logical OR).
The F_STATUS register must be read to determine which event(s) occurred.
To clear this flag, both F_OVF and F_WMKF flags must be cleared. See F_STATUS for details.
0: FIFO Event not detected
1: FIFO Event was detected
4:0
FE_TIME
Number of ODR periods elapsed since F_EVENT was set
Indicates the number of samples acquired since a FIFO event flag (overflow or watermark) was
asserted.
Reset when F_OVF and F_WMKF fall.
To clear this field, the F_EVENT flag must be cleared.
6.7 0x0B: INT_SOURCE_FLAG
The INT_SOURCE_FLAG register provides the event-flag status for the interrupt
generating functions within the device. Reading the INT_SRC_FLAG register does
not reset any event-flag source bits; they are reset by reading the appropriate event
source register.
Table 28. INT_SRC register
Bit76543210
Read 0 0 0 0 BOOTEND SRC_FIFO SRC_RT SRC_DRDY
Write
Reset00000000
Table 29. INT_SRC_FLAG field descriptions
Field Description
3
BOOTEND
Boot sequence complete event flag
Asserted as soon as the device boot sequence has completed and remains at '1' thereafter.
1: Boot sequence is complete
0: When one of the following occurs:
A hard or soft reset event is triggered
A POR event occurs
Table continues on the next page...
Register Descriptions
37
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 29. INT_SRC_FLAG field descriptions
(continued)
Field Description
2
SRC_FIFO
FIFO event source flag
Indicates that the FIFO event flags triggered the interrupt
1: When the FIFO event flag F_Event[F_Event] is set (F_OVF or F_WMKF are set), provided the FIFO
interrupt is enabled (CTRL_REG2[INT_EN_FIFO] = 1).
0: Cleared when F_Event flag gets cleared (whenever both F_OVF and F_WMKF get cleared).
1
SRC_RT
Rate threshold event source flag
Indicates that the rate threshold event flag(s) triggered the interrupt
1: When the event active flag RT_SRC[EA] is set, provided the Rate Threshold interrupt is enabled
(CTRL_REG2[INT_EN_RT] = 1).
0: Cleared when the event active flag RT_SRC[EA] is cleared.
0
SRC_DRDY
Data-ready event source flag
Indicates that a data-ready event triggers the interrupt
1: When any of the data-ready flags from DR_STATUS are set, provided the Data Ready interrupt is
enabled (CTRL_REG2[INT_EN_DRDY] = 1).
0: Cleared by reading the MSBs of the X, Y, and Z axes sample data.
6.8 0x0C: WHO_AM_I
The WHO_AM_I register contains the device identifier which is factory programmed to
0xD7.
Table 30. WHO_AM_I
Bit76543210
Read WHO_AM_I[7:0]
Write
Reset11010111
6.9 0x0D: CTRL_REG0
CTRL_REG0 is used for general control and configuration of the device. The bit fields
in CTRL_REG0 should be changed only in Standby or Ready modes. Accuracy of the
output data is not guaranteed if these bits are changed when the device is in Active
mode.
Register Descriptions
38
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 31. CTRL_REG0
Bit76543210
Read BW[1:0] SPIW SEL[1:0] HPF_EN FS[1:0]
Write
Reset00000000
Table 32. CTRL_REG0 field descriptions
Field Description
7:6
BW
Bandwidth
Selects the cut-off frequency of the digital low-pass filter, limiting the bandwidth of the digital
output data as shown in Table 33.
5
SPIW
SPI interface mode selection
0: SPI 4-wire mode (default)
1: SPI 3-wire mode (MOSI pin is used for SPI input and output signals)
4:3
SEL
High-pass filter cutoff frequency selection
Details of the high-pass filter settings are shown in Table 34.
2
HPF_EN
High-pass filter enable
The high-pass filter is initialized on operating mode and ODR change.
When enabled, the HPF is applied to the angular rate data supplied to the output registers/FIFO
and the embedded rate threshold function.
0: High-pass filter disabled (default)
1: High-pass filter enabled
1:0
FS
Full-scale range selection
See Table 35
Table 33. FXAS21002C LPF cutoff frequency
BW ODR = 800
Hz
ODR = 400
Hz
ODR = 200
Hz
ODR = 100
Hz
ODR = 50 Hz ODR = 25 Hz ODR = 12.5 Hz
0b00 256 128 64 32 16 8 4
0b01 128 64 32 16 8 4
0b1x 64 32 16 8 4
Table 34. High-pass filter cutoff frequency selection
SEL1 SEL0 Cutoff Frequency in Hz versus ODR
800 Hz 400 Hz 200 Hz 100 Hz 50 Hz 25 Hz 12.5 Hz
0 0 15 7.5 3.75 1.875 0.937 0.468 0.234
0 1 7.7 3.85 1.925 0.963 0.481 0.241 0.120
1 0 3.9 1.95 0.975 0.488 0.244 0.122 0.061
1 1 1.98 0.99 0.495 0.248 0.124 0.062 0.031
Register Descriptions
39
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
HPF_EN enables the high pass filter. Note that high-pass filter is initialized on mode
change, ODR change, and assertion of the zero rate register bit. When enabled, the
high-pass filtered data is input to both the output data registers/FIFO and the rate
threshold function.
FS[1:0] selects the full scale range of the device as shown in Table 35.
Table 35. Selectable Full Scale Ranges
FS1 FS0 Range (dps) Nominal Sensitivity (mdps/LSB)
0 0 ±2000 62.5
0 1 ±1000 31.25
1 0 ±500 15.625
1 1 ±250 7.8125
NOTE
Setting the CTRL_REG3[FS_DOUBLE] increases the
dynamic range for each CTRL_REG0[FS] selection by a
factor of two, from ±250/500/1000/2000°/s to
±500/1000/2000/4000°/s.
6.10 0x0E: RT_CFG
The RT_CFG register is used to enable the Rate Threshold interrupt generation. The
internal state of the Rate Threshold function is reset when a transition from Standby to
Active or Ready to Active modes occurs. The contents should only be modified when
the device is in Standby mode.
Table 36. RT_ CFG Register
Bit76543210
Read 0 0 0 0 ELE ZTEFE YTEFE XTEFE
Write
Reset00000000
Register Descriptions
40
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 37. RT_CFG field descriptions
Field Description
3
ELE
Event latch enable
See Functionality for more details.
0: Event flag latch disabled
1: Event flag latch enabled
2
ZTEFE
Event flag enable on Z-axis rate
Enable bits for rate threshold event detection on the Z axis
0: Z event detection disabled
1: Z Event detection enabled
1
YTEFE
Event flag enable on Y-axis rate
Enable bits for rate threshold event detection on the Y axis
0: Y event detection disabled
1: Y Event detection enabled
0
XTEFE
Event flag enable on X-axis rate
Enable bits for rate threshold event detection on the X axis
0: X event detection disabled
1: X Event detection enabled
6.11 0x0F: RT_SRC
This register indicates the source of the Rate Threshold event. The content of
RT_SRC is reset upon a transition from Standby to Active or from Ready to Active
modes.
Table 38. RT_ SRC Register
Bit76543210
Read 0 EA ZRT Z_RT_POL YRT Y_RT_POL XRT X_RT_POL
Write
Reset00000000
Register Descriptions
41
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 39. RT_SRC field descriptions
Field Description
6
EA
Event active flag
EA indicates that a rate threshold event has been detected on at least one of the axes (OR
condition). This bit is cleared after a read of this register only if it has been latched (ELE =1).
0: No event flags have been asserted
1: One or more event flags have been asserted (XRT, YRT or ZRT)
5
ZRT
Z rate event
Indicates that a rate threshold event (as defined in Functionality) has been detected on the Z-axis
(only if RT_CFG[ZTEFE] is 1).
Flag is asserted a few samples (RT_COUNT) after the absolute value of the Z output rate data
goes above the RT_THS value.
Cleared a few samples (RT_COUNT) after the absolute value of Z rate output goes below the
RT_THS value. Also cleared when the register is read, if it has been latched (ELE = 1).
0: No rate threshold event detected on Z axis
1: Rate Threshold event detected on Z axis
4
Z_RT_POL
Polarity of Z event
Indicates the rate polarity on the Z-axis (if RT_CFG[ZTEFE] =1). If RT_CFG[ZTEFE] =1, this bit
indicates the polarity of the Z data irrespective of the rate threshold event detected on Z-axis.
Cleared when read if it has been latched (ELE =1)
0: Z rate event was Positive
1: Z rate event was Negative
3
YRT
Y rate event
Indicates that a rate threshold event (as defined in Functionality) has been detected on the Y-axis
(only if RT_CFG[YTEFE] =1).
Flag is asserted few samples(RT_COUNT) after the absolute value of the Y output rate data goes
above the RT_THS value.
Cleared a few samples (RT_COUNT) after the absolute value of Y rate output goes below the
RT_THS value. Also cleared when the register is read if it has been latched (ELE = 1).
0: No Rate Threshold event detected on Y axis
1: Rate Threshold event detected on Y axis
2
Y_RT_POL
Polarity of Y event
Indicates the rate polarity on the Y-axis (if RT_CFG[YTEFE] =1). If RT_CFG[YTEFE] =1, this bit
indicates the polarity of the Y data irrespective of the rate threshold event detected on Y-axis.
Cleared when read if it has been latched (ELE =1)
0: Y rate event was Positive
1: Y rate event was Negative
Table continues on the next page...
Register Descriptions
42
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 39. RT_SRC field descriptions (continued)
Field Description
1
XRT
X rate Event
Indicates that a rate threshold event (as defined in Functionality) has been detected on the X-axis
(only if RT_CFG[XTEFE] =1).
Flag is asserted few samples (RT_COUNT) after the absolute value of the X output rate data goes
above the RT_THS value.
Cleared a few samples (RT_COUNT) after the absolute value of X rate output goes below the
RT_THS value. Also cleared when the register is read if it has been latched (ELE = 1).
0: No Rate Threshold event detected on X axis
1: Rate Threshold event detected on X axis.
0
X_RT_POL
Polarity of X event
Indicates the rate polarity on the X axis (if RT_CFG[XTEFE] =1). If RT_CFG[XTEFE] =1, this bit
indicates the polarity of the X-data irrespective of the rate threshold event detected on X-axis.
Cleared when read if it has been latched (ELE =1)
0: X rate event was positive
1: X rate event was negative
6.12 0x10: RT_THS
The RT_THS register sets the threshold limit for the detection of the rate and the
debounce counter mode. See Functionality for more details.
Table 40. RT_THS register
Bit76543210
Read DBCNTM THS[6:0]
Write
Reset00000000
Table 41. RT_THS field descriptions
Field Description
7
DBCNTM
Debounce counter mode selection
The contents should only be modified when the device is in Standby mode
1: Clear counter when angular rate is below the threshold value
0: Decrement counter on every ODR cycle that the angular rate is below the threshold value
Table continues on the next page...
Register Descriptions
43
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 41. RT_THS field descriptions (continued)
Field Description
6:0
THS
Unsigned 7-bit rate threshold value
The contents should only be modified when the device is in Standby mode
The internal state of the Rate Threshold function is reset when a transition from Standby to Active
or Ready to Active modes occurs.
The rate threshold in dps is given by the following formula:
Rate Threshold (dps) = (THS+1) * 256 * Sensitivity (dps/LSB)
Rate Threshold (LSB) = (THS+1) * 256
NOTE
The sensitivity (dps/LSB) varies with the FSR setting:
CTRL_REG0[FS] and also with the FS_DOUBLE setting:
CTRL_REG3[FS_DOUBLE]. See Table 54 for more
sensitivity details on enabling FS_DOUBLE.
6.13 0x11: RT_COUNT
RT_COUNT sets the number of debounce counts. See Functionality for more details.
Table 42. RT_COUNT register
Bit76543210
Read RT_CNT[7:0]
Write
Reset00000001
Table 43. RT_COUNT field descriptions
Field Description
7:0
RT_CNT
Debounce counter value
The contents should only be modified when the device is in Standby mode
The internal state of the Rate Threshold function debounce counter is reset when a transition from
Standby to Active or Ready to Active modes occurs
Stores the number of counts with the angular rate above the threshold needed before asserting the
rate threshold event flag
The counter period is the same as the selected ODR period, allowing for a debounce time to be
calculated. For example, an RT_COUNT value of 10 (decimal) and an ODR of 100 Hz would result
in a debounce time of 100 ms.
Register Descriptions
44
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
6.14 0x12: TEMP
The TEMP register contains an 8-bit 2's complement temperature value with a range
of –128 °C to +127 °C and a scaling of 1 °C/LSB. The temperature data is only
compensated (factory trim values applied) when the device is operating in the Active
mode and actively measuring the angular rate.
Table 44. TEMP register
Bit76543210
Read TEMP[7:0]
Write
Reset00000000
6.15 0x13: CTRL_REG1
The CTRL_REG1 register is used to configure the device ODR, set the operating
mode, soft-reset the device, and exercise the Self-Test function.
NOTE
Control bits in CTRL_REG1 should be changed only in
Standby or Ready mode. Accuracy of the output data is not
guaranteed if these bits are changed while the device is in
Active mode.
Table 45. CTRL_REG1 register
Bit76543210
Read RST ST DR[2:0] ACTIVE READY
Write
Reset00000000
Table 46. CTRL_REG1 field descriptions
Field Description
6
RST
Software Reset:
Used to trigger a reset of the device.
On reset, all registers except 0x01 through 0x06 revert to their default values. Register addresses
0x01 through 0x06 contain values that cannot be determined.
This bit is self cleared after assertion.
0: Device reset not triggered/completed
1: Device reset triggered
Table continues on the next page...
Register Descriptions
45
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 46. CTRL_REG1 field descriptions (continued)
Field Description
5
ST
Self-Test enable
When ST is set, a data output change will occur even if no angular rate is applied. This allows the
host application to check the functionality of the sensor and the entire measurement signal chain.
The expected Self-Test delta value is summarized in Table 4
0: Self-Test disabled
1: Self-Test enabled
4:2
DR
Output Data Rate selection
Selects the output data rate as per Table 47
1
Active Standby/Active mode selection, see Table 48
0
Ready Standby/Ready mode selection, see Table 48
NOTE
On issuing a Software Reset command over an I2C interface,
the device immediately resets and does not send any
acknowledgment (ACK) of the written byte to the Master.
Table 47. Digital output data bandwidth settings
Decimal number CTRL_REG1[DR] ODR (Hz)
0 000 800
1 001 400
2 010 200
3 011 100
4 100 50
5 101 25
6 110 12.5
7 111 12.5
The ACTIVE and READY bits are used to control the device operating mode. In
Standby mode (ACTIVE = 0), the device is only capable of communication on the I2C
or SPI digital interfaces. In Ready mode (READY = 1), the device is ready to measure
angular rate but no data acquisitions are being made. The Ready mode can be used to
reduce the device power consumption and allow for a fast transition into the Active
mode when needed. In Active mode (ACTIVE = 1), the device is fully functional. The
ACTIVE bit has a higher priority than the READY bit as shown in Table 48.
Register Descriptions
46
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 48. Device operating mode
Active Ready Operating mode
0 0 Standby
0 1 Ready
1 X Active
When CTRL_REG3[EXTCTRLEN] = 1, the ACTIVE bit is directly controlled by
the logic level input to the INT2/PWR_CTRL pin and becomes read-only via the
register interface. Thus, the device operating mode can be directly controlled by the
INT2/PWR_CTRL pin when CTRL_REG3[EXTCTRLEN] =1. The weak pull-up
resistor is internal to the IC and automatically enabled when
CTRL_REG3[EXTCTRLEN] is set to 1, hence setting the Active bit high.
6.16 0x14: CTRL_REG2
This register enables and assigns the output pin(s) and logic polarities for the various
interrupt sources available on the device.
Table 49. CTRL_REG2 register
Bit 7 6 5 4 3 2 1 0
Read INT_CFG_FIFO INT_EN_FIFO INT_CFG_RT INT_EN _RT INT_CFG_DRDY INT_EN_DRDY IPO
L
PP_O
D
Write
Reset 0 0 0 0 0 0 0 0
Table 50. Interrupt Enable register descriptions
Register Description
7
INT_CFG_FIFO
FIFO interrupt pin routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
6
INT_EN_FIFO
FIFO Interrupt Enable
0: FIFO interrupt disabled
1: FIFO interrupt enabled
Table continues on the next page...
Register Descriptions
47
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
Table 50. Interrupt Enable register descriptions (continued)
Register Description
5
INT_CFG_RT
Rate threshold interrupt pin routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
4
INT_EN_RT
Rate threshold interrupt enable
0: Rate threshold interrupt disabled
1: Rate threshold interrupt enabled
3
INT_CFG_DRDY
Data-ready interrupt pin routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
2
INT_EN_DRDY
Data ready interrupt enable
0: Data-ready interrupt disabled
1: Data-ready interrupt enabled
1
IPOL
Interrupt logic polarity
0: Active low
1: Active high
0
PP_OD
INT1 and INT2 pin output driver configuration
0: Push-pull output driver
1: Open-drain/open-source buffer with IPOL = 0/1, respectively
Table 51. INT pin behavior as a function of PP_OD and IPOL bit settings
INT pin configuration PP_OD IPOL INT asserted value INT deasserted value
CMOS output 0 0 0 1
CMOS output 0 1 1 0
External pull-up resistor added 1 0 0 High-z1
External pull-down resistor added 1 1 1 High-z1
1. High-z = tri-state (high impedance) condition; the state of the INT pin will be defined by the external pull-up or pull-down
resistor.
6.17 0x15:CTRL_REG3
This register is used to enable the FSR expansion, external power control input, and
options to modify the auto-increment read address pointer behavior when doing burst
reads of the FIFO data.
Register Descriptions
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Table 52. CTRL_REG3 register
Bit 7 6 5 4 3 2 1 0
Read WRAPTOONE EXTCTRLEN FS_DOUBLE
Write
Reset 0 0 0
NOTE
Control bits in CTRL_REG3 should only be changed when
operating in Standby or Ready mode. Accuracy of the output
data is not guaranteed if any of these bits are changed while
the device is operating in Active mode.
Table 53. CTRL_REG3 register descriptions
Register Description
3
WRAPTOONE
Auto-increment read address pointer roll-over behavior:
0: The auto-increment read address pointer rolls over to address 0x00 (STATUS) after the Z-axis
LSB is read (default).
1: The auto-increment pointer rolls over to address 0x01 (X-axis MSB) in order to facilitate the faster
read out of the FIFO data in a single burst read operation (STATUS register only needs to be read
once).
2
EXTCTRLEN
External power mode control input:
0: INT2 pin is used as an interrupt output (default)
1: INT2 pin becomes an input pin that may be used to control the power mode. Note that when
EXTCTRLEN is set, the interrupt outputs and related settings for the INT2 pin are ignored.
EXTCTRLEN allows the device operating mode to be controlled using the INT2 pin (the pin
becomes a high impedance input when this bit is set high). The input is level sensitive, and allows
the host to transition the device operating mode from either Standby to Active or from Ready to
Active (and vice-versa) depending on the operating mode, Standby or Ready, that was configured at
the time this bit was set.
0
FS_DOUBLE
Full-scale range expansion enable:
0: Maximum full-scale range selections are as per Table 37, selected via the CTRL_REG0[FS] field.
1: Maximum full-scale range selections are doubled from what is shown in Table 37.
FS_DOUBLE increases the dynamic range for each CTRL_REG0[FS] selection by a factor of two,
from ±250/500/1000/2000°/s to ±500/1000/2000/4000°/s. This feature is provided to enable a higher
dynamic range for applications such as sports equipment monitoring (e.g. golf club or tennis racket
swings). While the full-scale range is doubled in this mode, the noise and nonlinearity of the signal
are also increased.
Register Descriptions
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Table 54. Rate sensitivity changes with FSR_DOUBLE
setting
FSR Selection Sensitivity (mdps/LSB)
FSR_DOUBLE = 0
Sensitivity (mdps/LSB)
FSR_DOUBLE = 1
CTRL_REG0[FS] = 00 62.50 125.0
CTRL_REG0[FS] = 01 31.25 62.50
CTRL_REG0[FS] = 10 15.625 31.25
CTRL_REG0[FS] = 11 7.8125 15.625
7 Printed Circuit Board Layout and Device Mounting
Printed Circuit Board (PCB) layout and device mounting are critical to the overall
performance of the design. The footprint for the surface mount packages must be the
correct size as a base for a proper solder connection between the PCB and the package.
This, along with the recommended soldering materials and techniques, will optimize
assembly and minimize the stress on the package after board mounting.
Freescale application note AN1902, "Assembly Guidelines for QFN and DFN
Packages" discusses the QFN package used by the FXAS21002C.
7.1 Printed Circuit Board Layout
The following recommendations are meant to serve as general guidelines for realizing
an effective PCB layout. See Figure 24 for component PCB footprint dimensions.
The PCB land pattern should be designed with Non-Solder Mask Defined (NSMD)
as shown in Figure 24.
On the layer that the device is soldered, there should be no trace routing or vias
underneath the device's component package.
No components or vias should be placed at a distance less than 2 mm from the
package land area. This may cause additional package stress if it is too close to the
package land area.
Signal traces connected to pads should be as symmetric as possible. Put dummy
traces on the NC pads in order to have same length of exposed trace for all pads.
No copper traces should be on the top layer of the PCB under the package, as this
will cause planarity issues with the board mount. Freescale QFN sensors are
compliant with Restrictions on Hazardous Substances (RoHS), having halide-free
molding compound (green) and lead-free terminations. These terminations are
Printed Circuit Board Layout and Device Mounting
50
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
compatible with tin-lead (Sn-Pb) as well as tin-silver-copper (Sn-Ag-Cu) solder
paste soldering processes. Reflow profiles applicable to those processes can be
used successfully for soldering the devices.
PCB land pad
Solder stencil opening
24X 0.8
24X 0.3
20X 0.5
4X 2.175
Solder mask opening
4X 1.438
4.576
4X 1.938
4.576
Package
24X 0.769
24X 0.269
20X 0.5
4X 2.160
Package outline
Package outline
4
128
24X 0.30
0.18
4
24X 0.725
0.525
7
1
2024
13
19
20X 0.5 Package outline
Figure 24. Footprint
7.2 Overview of Soldering Considerations
The information provided here is based on experiments executed on QFN devices.
These experiments cannot represent exact conditions present at a customer site.
Therefore, information herein should be used for guidance purposes only. Process and
design optimizations are recommended to develop an application-specific solution.
With the proper PCB footprint and solder stencil designs, the package will self-align
during the solder reflow process.
Stencil thickness should be 100 or 125 µm.
Printed Circuit Board Layout and Device Mounting
51
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Freescale Semiconductor, Inc.
The PCB should be rated for the multiple lead-free reflow condition with a
maximum 260 °C temperature.
Use a standard pick-and-place process and equipment. Do not use a hand soldering
process.
Do not use a screw-down or stacking to mount the PCB into an enclosure. These
methods could bend the PCB, which would put stress on the package.
7.3 Halogen Content
This package is designed to be Halogen Free, exceeding most industry and customer
standards. Halogen Free means that no homogeneous material within the assembled
package will contain chlorine (Cl) in excess of 700 ppm or 0.07% weight/weight or
bromine (Br) in excess of 900 ppm or 0.09% weight/weight.
8 Package Information
The FXAS21002C platform uses a 24-lead QFN package, case number 2209-01.
8.1 Product Identification Markings
Top View
263
F2102
ALYW
Traceability date code
Assembly site
Lot code
Work week
Part number
Freescale code
Package Information
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Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
8.2 Tape and Reel Information
Figure 25. Tape dimensions
Barcode label
side of reel
Pin 1
Direction
to unreel
Figure 26. Tape and reel orientation
Package Information
53
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Freescale Semiconductor, Inc.
8.3 Package Description
This drawing is located at www.freescale.com/files/shared/doc/package_info/98ASA00356D.pdf.
Package Information
54
Freescale Semiconductor, Inc.
3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
9 Revision History
Revision
number
Revision
date Description
0.3 3/2014 Initial release of document
1.0 8/2014 Added the following sections:
Mechanical and Electrical Specifications
Digital Interfaces
Modes of Operation
Functionality
Register Descriptions
Printed Circuit Board Layout and Device Mounting
1.1 11/2014 Figure 1, removed BYP
Table 2, removed T = 25°C from Test conditions
Table 6, removed "Sensitivity error due to linear acceleration removed Zero Rate Offset
error due to linear acceleration Added footnote to Zero-rate Offset, Post-Board Mount"
Section 5.2, image, added Latch and ELE connection
Section 6.4, removed "Reading F_STATUS clears the SRC_FIFO bit in the 0x0B:
INT_SOURCE_FLAG register."
Table 27, F_EVENT field, added bullet: To clear this flag, both F_OVF and F_WMKF
flags must be cleared. See F_STATUS for details.
Table 27, F_EVENT field, added bullet: To clear this field, the F_EVENT flag must be
cleared.
Table 29, SRC_FIFO field, changed flag descriptions from
1: F_OVF or F_WMKF are set, provided the FIFO interrupt is enabled
(CTRL_REG2[INT_EN_FIFO=1])
0: Cleared by reading the register
to
1: When F_Event flag is set (F_OVF or F_WMKF are set), provided the FIFO interrupt
is enabled (CTRL_REG2[INT_EN_FIFO=1])
0: Cleared when F_Event Flag gets cleared (whenever both F_OVF and F_WMKF get
cleared)
Table 29, SRC_RT field, changed bullets from
Indicates that the rate threshold event flag triggered the interrupt
Cleared by reading RT_SRC register
to
Indicates that the rate threshold event flag(s) triggered the interrupt (when XRT or
YRT or ZRT(logical OR) event threshold flags go high)
Cleared when XRT, YRT or ZRT event threshold flags are cleared.
Section 6.11, added: "It also clears the RT_SRC flag in the 0x0B: INT_SOURCE_FLAG
register."
Added Table 54, Rate sensitivity changes with FSR_DOUBLE setting
1.2 11/2014 Removed last two features items
Minor changes to table 2, Temperature Sensor Characteristics
In Mechanical Characteristics table, changed typical parameters for Zero-rate Offset,
Zero-rate Offset, Post-board Mount and Integral nonlinearity and updated table
footnotes.
Table continues on the next page...
Revision History
55
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Freescale Semiconductor, Inc.
Revision
number
Revision
date Description
Updated Electrical Charactristics table, for Supply current drain in Standby mode, and
Supply current drain in Standby mode over Temperature parameters. Also removed
test condition on Output Data Rate frequency tolerance parameter.
Changed Table 8 Serial interface pin descriptions, pin currently named SDA/MOSI/
SPI_Data and modified pin description.
changed Table 9, Slave timing values, for parameter SDA and SCL fall time, minimum
values for I2C Fast Mode.
Added table title to Table 10. I2C Register Data Address Map.
Section 3.1.1, I²C Operation, changed first paragraph to read “External pull-up resistors
connected to VDDIO”...
Section 5, functionality, changed seventh bullet to read “Embedded rate threshold
detection function with programmable debounce time”
Added new column “Auto-Increment Address” to Table 13 Register address map and
populated the column with data. Removed last two rows of table, Auto-Increment
address and Fast-read increment address.
Modified note after Table 19 to read “After this register is read, the next read register by
the autoincrement process is STATUS at 0x00, when CTRL_REG3[WRAPTOONE] = 0,
or OUT_X_MSB when CTRL_REG3[WRAPTOONE] = 1.”
2.0 2/2015 Moved Section 2.1 to 2.5
Figure 12, changed "SPI_DIO" to "SPI_DATA"
Register 0x09: F_SETUP, added "The contents should only be modified when the
device is in Standby mode."
Table 29, Field 1, changed "...XRT, YRT or ZRT..." to "...XRT, YRT and ZRT..."
Register 0x0E: RT_CFG, added "The internal state of the Rate Threshold function is
reset when..."
Table 37, Field 3, deleted second and third bullet
Register 0x0F: RT_SRC, added "The content of this register is reset upon a transition
from Standy to Active or from Ready to Active modes.
Table 39:
Field 6
added "only if it has been latched (ELE =1)"
added to bit 1 "(XRT, YRT or ZRT)"
Field 5
changed second bullet to "Flag is asserted few samples (RT_COUNT)..."
added third bullet "Cleared when the absolute value of Z..."
changed bit 0 from "Z rate lower than RT_THS value" to "No rate threshold event
detected on Z-axis"
changed bit 1 from "Z rate greater than RT_THS event has occured" to "Rate
Threshold event detected on Z axis"
Field 4
changed first bullet from "Indicates the rate polarity on the Z-axis (if ZTEFE =1). If
ZTEFE =1, this bit indicates the polarity of the Z data irrespective of the rate
threshold event detected on Z-axis." to "Indicates the rate polarity on the Z-axis (if
RT_CFG[ZTEFE] =1). If RT_CFG[ZTEFE] =1, this bit indicates the polarity of the
Z data irrespective of the rate threshold event detected on Z-axis."
Field 3
changed second bullet to "Flag is asserted few samples (RT_COUNT)..."
added third bullet "Cleared when the absolute value of Y..."
changed bit 0 from "Y rate lower than RT_THS value" to "No rate threshold event
detected on Y-axis"
changed bit 1 from "Y rate greater than RT_THS event has occured" to "Rate
Threshold event detected on Y-axis"
Field 2
Table continues on the next page...
Revision History
56
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3-Axis Digital Angular Rate Gyroscope, Rev. 2.1, 5/2015
Revision
number
Revision
date Description
changed first bullet from "Indicates the rate polarity on the Y-axis (if YTEFE =1). If
YTEFE =1, this bit indicates the polarity of the Y data irrespective of the rate
threshold event detected on Y-axis." to "Indicates the rate polarity on the Y-axis
(if RT_CFG[YTEFE] =1). If RT_CFG[YTEFE] =1, this bit indicates the polarity of
the Y data irrespective of the rate threshold event detected on Y-axis."
Field 1
changed second bullet to "Flag is asserted few samples (RT_COUNT)..."
added third bullet "Cleared when the absolute value of X..."
changed bit 0 from "X rate lower than RT_THS value" to "No rate threshold event
detected on X-axis"
changed bit 1 from "X rate greater than RT_THS event has occured" to "Rate
Threshold event detected on X-axis"
Field 0
changed first bullet from "Indicates the rate polarity on the X-axis (if XTEFE =1). If
XTEFE =1, this bit indicates the polarity of the X data irrespective of the rate
threshold event detected on X-axis." to "Indicates the rate polarity on the X-axis
(if RT_CFG[XTEFE] =1). If RT_CFG[XTEFE] =1, this bit indicates the polarity of
the X data irrespective of the rate threshold event detected on X-axis."
Table 41, Field 6:0, changed formula from "Rate_threshold=THS*(Full_scale/128)" to
"Rate Threshold (in dps) = (THS + 1)* 256 * Sensitivity (in dps/LSB)" and
"Rate_Threshold(in LSB) = (THS + 1)* 256"
2.1 5/2015 Table 5, Self-test output change, Min value of 7000 added and Max value of 25000
added
Table 6
Digital high level input voltage, added SCLK
Low-level output voltage, added test condition of lo = 1 mA
Section 5, second bullet, changed CTRL_REG3[FSR_DOUBLE] = 1 to
CTRL_REG3[FS_DOUBLE] = 1
Table 13
F_EVENT, added the default value of 0x00
INT_SRC_FLAG, added the default value of 0x00
CTRL_REG3, changed Auto-increment address from 0x16 to 0x00
RESERVED, added Auto-increment address of address + 1
Revision History
57
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Freescale Semiconductor, Inc.
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and/or specifications can and do vary in different applications, and
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© 2014-2015 Freescale Semiconductor, Inc.
Document Number FXAS21002C
Revision 2.1, 5/2015