2014 Microchip Technology Inc. DS40001762A-page 1
MCS3122
Features Overview
• Advanced KEELOQ® Technology:
- Programmable 32-bit serial number
- Programmable 32-bit serial number for seed
transmissions
- AES-128 block cipher
- Programmable 128-bit crypt key
- 160/192-bit transmission code length:
- 32-bit unencrypted portion
- 128-bit encrypted, code hopping portion
- 32-bit authorization check (optional)
• Operating Features:
- 2.0 to 3.7V operation
- Three switch inputs
- Seven functions available
- One active-low LED drive
- Configurable maximum code word
•RF:
- Configurable bit rate
- Configurable modulation, supporting FSK
and OOK
- Configurable data modulation, supporting
PWM and Manchester
•Other:
- Button inputs have internal pull-up resistors
Typical Applications
MCS3122 is ideal for Remote Keyless Entry (RKE)
applications. These applications include:
• Automotive RKE Systems
• Automotive Alarm Systems
• Gate and Garage Door Openers
• Home Security Systems
• Security and Safety Sensors
• Remote Control
• Remote Keypad
• Wireless Sensors
Package Type
• 14-Pin TSSOP
FIGURE 1: 14-PIN TSSOP
1
2
3
4
5
6
7
VDD
LED
CTRL_OUT
SW2
VDD
CTRL_IN
RFOUT
SW0
SW1
DATA_OUT
XTAL
DATA_IN
VSS
14
13
12
11
10
9
8
VSS
MCS3122
TABLE 1: PIN DESCRIPTION
Name 14-Pin TSSOP Input Type Output Type Description
VDD 1 Power — Power
LED 2 — TTL LED Output (active-low)
CTRL_OUT 3 — TTL Transmitter Clock
SW2 4 TTL — Switch 2 Input
VDD 5 Power — Power
CTRL_IN 6 TTL — Transmitter Clock
RFOUT 7 — RF Transmitter Output
VSS 8 Power — Power
DATA_IN 9 TTL — Transmitter Data
XTAL 10 Analog — Transmitter Reference Oscillator
DATA_OUT 11 — TTL Transmitter Data
SW1 12 TTL — Switch 1 Input
SW0 13 TTL — Switch 0 Input
VSS 14 Power — Power
MCS3122 Adv anced K
EE
L
OQ®
Technology Encoder Data Sheet
MCS3122
DS40001762A-page 2 2014 Microchip Technology Inc.
Table of Contents
1.0 General Description ................................................................................................................................................................... 3
2.0 Device Description .................................................................................................................................................................... 4
3.0 Memory Organization................................................................................................................................................................. 5
4.0 Advanced KEELOQ® Technology Operation............................................................................................................................... 9
5.0 Transmitter Operation.............................................................................................................................................................. 12
6.0 Integrating MCS3122 into a System ........................................................................................................................................ 15
7.0 Electrical Specifications ........................................................................................................................................................... 17
8.0 Packaging Information ............................................................................................................................................................. 18
The Microchip Web Site ....................................................................................................................................................................... 23
Customer Change Notification Service ................................................................................................................................................ 23
Customer Support ................................................................................................................................................................................ 23
Product Identification System .............................................................................................................................................................. 24
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2014 Microchip Technology Inc. DS40001762A-page 3
MCS3122
1.0 GENERAL DESCRIP T ION
MCS3122 is a KEELOQ encoder, designed for secure
Remote Keyless Entry (RKE) and secure remote
control systems. MCS3122 utilizes the Advanced
KEELOQ code hopping technology. The encoder
incorporates a high- security, low-cost small package
outline to make this device the perfect solution for
unidirectional authentication systems and access
control systems.
The Advanced KEELOQ technology uses the industry
standard AES-128 encryption algorithm, a serial
number and a message counter
which continuously
increments with each button press.
The crypt key, serial number and configuration data are
stored in a Flash array which is not accessible via any
external connection. The Flash data is programmable
but read-protected. The data can be verified only after
an automatic erase and programming operation. This
protects against attempts to gain access to keys or
manipulate synchronization values.
In addition,
MCS3122 provides an easy to use serial interface for
programming the necessary keys, system parameters
and configuration data.
1.1 Key Terms
The following is a list of key terms used throughout this
data sheet. For additional information on KEELOQ
technology and code hopping, refer to “An Intro duc tio n
to KEELOQ® Code Hopping” Technical Brief (DS91002).
•RKE: Remote Keyless Entry
•Function Code: It indicates what button input(s)
activated the transmission. It encompasses the
function code bits.
•Code Hopping: A method by which a code,
viewed externally to the system, appears to
change unpredictably each time it is transmitted.
•Code Word: A block of data that is repeatedly
transmitted upon button activation.
•Transmission: A data stream consisting of
repeating code words.
•Crypt Key: A unique and secret number (128-bit
for Advanced KEELOQ technology) used to
encrypt and decrypt data. In a symmetrical block
cipher such as those used on MCS3122, the
encryption and decryption keys are equal and,
therefore, will generally be referred to as the crypt
key.
•Encoder: A device that generates and encodes
data.
•Encryption Algorithm: A method whereby data
is scrambled using a crypt key. The data can only
be interpreted by the respective decryption
algorithm using the same crypt key.
•Decoder: A device that decodes data received
from an encoder.
•Decryption Algorithm: A recipe whereby data,
scrambled by an encryption algorithm, can be
unscrambled using the same crypt key.
•Learn: Learning involves the receiver calculating
the transmitter’s appropriate crypt key, decrypting
the received hopping code and storing the serial
number, synchronization counter or timer value,
and crypt key in EEPROM. The KEELOQ
technology product family facilitates several
learning strategies to be implemented on the
decoder. The following are examples of what can
be done:
-Simple Learning: The receiver uses a fixed
crypt key. The crypt key is common to every
component used by the same manufacturer.
-Normal Learning: The receiver derives a
crypt key from the encoder serial number.
Every transmitter has a unique crypt key.
-Secure Learning: The receiver derives a
crypt key from the encoder seed value. Every
encoder has a unique seed value that is only
transmitted by a special button combination.
•Manufacturer’s Code: A unique and secret
number (128-bit for Advanced KEELOQ
technology) used to derive crypt keys. Each
encoder is programmed with a crypt key that is a
function of the manufacturer’s code. Each
decoder is programmed with the manufacturer’s
code itself.
The MCS3122 code hopping encoder is designed
specifically for keyless entry systems. Typical
applications include vehicles and home garage door
openers. The encoder portion of a keyless entry system
is integrated into a transmitter carried by the user. The
transmitter is operated to gain access to a vehicle or a
restricted area. MCS3122 is meant to be a cost-
effective, yet secure solution to such systems, requiring
very few external components (see Figure 2-1).
Most low-end keyless entry transmitters are given a
fixed identification code that is transmitted every time a
button is pushed. The number of unique identification
codes in a low-end system is usually a relatively small
number. These shortcomings provide an opportunity
for a sophisticated thief to create a device that ‘grabs’
a transmission and retransmits it later, or a device that
quickly ‘scans’ all possible identification codes until the
correct one is found.
Advanced KEELOQ technology uses the industry
standard AES-128 encryption algorithm to obscure
data using 128 bits for both its block and key length. In
addition to the security of Advanced KEELOQ
technology, the encoder sends a message
authorization block which is used to separate the
message encryption from the message authentication.
MCS3122
DS40001762A-page 4 2014 Microchip Technology Inc.
2.0 DEVICE DESCRIPTION
As shown in the typical application circuit (Figure 2-1),
MCS3122 is a simple device to use. It requires only the
addition of up to three buttons, a transmitter reference
oscillator, and RF circuitry for use as the transmitter in
the security application. See Tab le 1 for a description of
each pin.
FIGURE 2-1: TYPICAL CIRCUIT
XTAL
B1
B0
B2
LED
VDD
VDD
Matching
Circuit
Block
VDD VSS
LED
CTRL_OUT
SW2
VDD
CTRL_IN
RFOUT
SW0
SW1
DATA_OUT
XTAL
DATA_IN
VSS
2014 Microchip Technology Inc. DS40001762A-page 5
MCS3122
3.0 MEMORY ORGANIZATION
MCS3122 has 64 bytes of configuration data. In
general, the Configuration bytes can be divided into
two categories: those options related to the Advanced
KEELOQ technology encoder and those related to the
transmitter and device operation.
3.1 Counter and Protection
The synchronization counter is read, checked for
integrity, updated (incremented) and saved back to
Flash during normal operation of the device. The
special operation prevents against data loss from
unexpected power loss. An 8-bit checksum is
calculated and stored alongside the synchronization
counter. The checksum is calculated as a two’s
complement checksum. If there is a mismatch, the
second copy of the synchronization counter is read
instead. Example 3-1 illustrates how to compute this
value.
EXAMPLE 3-1: CHECKSUM CALCULA TION
TABLE 3-1: CONFIGURATION REGISTERS
Address Size (Bytes) Descripti on
0x00-0x02 3 Synchronization Counter, Copy A
0x03 1 Synchronization Counter Checksum
0x04-0x07 4 Reserved (set to 0xFF)
0x08-0x0A 3 Synchronization Counter, Copy B
0x0B 1 Reserved (set to 0xFF)
0x0C-0x0F 4 Seed Transmission Serial Number (usually set to 0xFFFFFFFF)
0x10-0x1F 16 Encryption Key
0x20-0x2F 16 Authorization Key
0x30-0x33 4 Serial Number
0x34-0x35 2 Transmitter Settings
0x36-0x37 2 Reserved (set to 0xFF)
0x38-0x3F 8 Seed Value
static uint8_t crc(const uint8_t* buffer, size_t len){
uint8_t bitcount;
uint8_t checksum = 0xFF;
while(len--)
{
c = c + *buffer++;
}
return 0-c;
}
MCS3122
DS40001762A-page 6 2014 Microchip Technology Inc.
3.2 Configuration Byte Details
The following tables describe Configuration bytes in
detail.
TABLE 3-2: ADVANCED KEELOQ® TECHNOLOGY SYNCHRONIZATION REGISTERS, COPY A
Byte Address Bit Description Values
0x00 7:0 Synchronization
Counter, Copy A
Byte 0 of the synchronization counter (LSB)
0x01 7:0 Byte 1 of the synchronization counter
0x02 7:0 Byte 2 of the synchronization counter (MSB)
0x03 7:0 Checksum Checksum of the synchronization counter
TABLE 3-3: ADVANCED KEELOQ® TECHNOLOGY SYNCHRONIZATION REGISTERS, COPY B
Byte Address Bit Description Values
0x08 7:0 Synchronization
Counter, Copy B
Byte 0 of the synchronization counter (LSB)
0x09 7:0 Byte 1 of the synchronization counter
0x0A 7:0 Byte 2 of the synchronization counter (MSB)
TABLE 3-4: ADVANCED KEELOQ® TECHNOLOGY SEED SERIAL NUMBER REGISTERS
Byte Address Bit Description Values
0x0C 7:0 Seed Serial Number Byte 0 of the seed serial number (LSB)
0x0D 7:0 Byte 1 of the seed serial number
0x0E 7:0 Byte 2 of the seed serial number
0x0F 7:0 Byte 3 of the seed serial number (MSB)
TABLE 3-5: ADVANCED KEELOQ® TECHNOLOGY CRYPT KEY REGISTERS
Byte Address Bit Description Values
0x10 7:0 Crypt Key Byte 0 of the crypt key (LSB)
0x11 7:0 Byte 1 of the crypt key
0x12 7:0 Byte 2 of the crypt key
0x13 7:0 Byte 3 of the crypt key
0x14 7:0 Byte 4 of the crypt key
0x15 7:0 Byte 5 of the crypt key
0x16 7:0 Byte 6 of the crypt key
0x17 7:0 Byte 7 of the crypt key
0x18 7:0 Byte 8 of the crypt key
0x19 7:0 Byte 9 of the crypt key
0x1A 7:0 Byte 10 of the crypt key
0x1B 7:0 Byte 11 of the crypt key
0x1C 7:0 Byte 12 of the crypt key
0x1D 7:0 Byte 13 of the crypt key
0x1E 7:0 Byte 14 of the crypt key
0x1F 7:0 Byte 15 of the crypt key (MSB)
2014 Microchip Technology Inc. DS40001762A-page 7
MCS3122
TABLE 3-6: ADVANCED KEELOQ® TECHNOLOGY AUTHORIZATION KEY REGISTERS
Byte Address Bit Descrip tion Values
0x20 7:0 Authorization Key Byte 0 of the authorization key (LSB)
0x21 7:0 Byte 1 of the authorization key
0x22 7:0 Byte 2 of the authorization key
0x23 7:0 Byte 3 of the authorization key
0x24 7:0 Byte 4 of the authorization key
0x25 7:0 Byte 5 of the authorization key
0x26 7:0 Byte 6 of the authorization key
0x27 7:0 Byte 7 of the authorization key
0x28 7:0 Byte 8 of the authorization key
0x29 7:0 Byte 9 of the authorization key
0x2A 7:0 Byte 10 of the authorization key
0x2B 7:0 Byte 11 of the authorization key
0x2C 7:0 Byte 12 of the authorization key
0x2D 7:0 Byte 13 of the authorization key
0x2E 7:0 Byte 14 of the authorization key
0x2F 7:0 Byte 15 of the authorization key (MSB)
TABLE 3-7: ADVANCED KEELOQ® TECHNOLOGY SERIAL NUMBER REGISTERS
Byte Address Bit Description Values
0x30 7:0 Serial Number Byte 0 of the serial number (LSB)
0x31 7:0 Byte 1 of the serial number
0x32 7:0 Byte 2 of the serial number
0x33 7:0 Byte 3 of the serial number (MSB)
MCS3122
DS40001762A-page 8 2014 Microchip Technology Inc.
TABLE 3-8: TRANSMITTER CONFIGURATION REGISTERS
Byte Address Bit Description Values
0x34 7:6 FSK Frequency Deviation 11 – 200 kHz
10 – 100 kHz
01 – 75 kHz
10 – 50 kHz
5Output Power 0 – 0 dBm
1 – 10 dBm
4 Encoding 1 – PWM
0 – Manchester
3 Modulation 1 – OOK
0 – FSK
2:0 Frequency Select 000 – 315.00 MHz (only with 24 MHz crystal)
001 – 390.00 MHz
010 – 418.00 MHz
011 – 433.92 MHz
100 – 868.30 MHz
101 – 868.65 MHz
110 – 868.95 MHz
111 – 915.00 MHz
0x35 3
and
1:0
Seed Button Configuration 111 – Disabled, no seed option
110 – SW0
101 – SW1
100 – SW1 and SW0
011 – SW2
010 – SW2 and SW0
001 – SW2 and SW1
000 – SW3, SW2 and SW1
2 Authorization Code Enable 1 – Enabled
0 – Disabled
5:4 Baud Rate 11 – 200 µS
10 – 150 µS
11 – 100 µS
11 – 50 µS
7:6 Maximum Code Words 11 – 234 words
10 – 80 words
01 – 4 words
00 – No maximum limit
TABLE 3-9: ADVANCED KEELOQ® TECHNOLOGY SEED CONFIGURATION REGISTERS
Byte Address Bit Description Values
0x38 7:0 Seed Value Byte 0 of the seed value (LSB)
0x39 7:0 Byte 1 of the seed value
0x3A 7:0 Byte 2 of the seed value
0x3B 7:0 Byte 3 of the seed value
0x3C 7:0 Byte 4 of the seed value
0x3D 7:0 Byte 5 of the seed value
0x3E 7:0 Byte 6 of the seed value
0x3F 7:0 Byte 7 of the seed value (MSB)
2014 Microchip Technology Inc. DS40001762A-page 9
MCS3122
4.0 ADVANCED KEELOQ®
TECHNOLOGY OPERATION
4.1 Synchronization Counter
This is the 24-bit synchronization value that is used to
create the hopping code for transmission. This value
will be incremented after every transmission. The initial
value of the synchronization counter may be set via the
Synchronization Counter Initial Value registers (see
Table 3-2 and Table 3 - 3).
4.2 Function Code (Button Status
Code)
The function code is a bitmapped representation of the
state of each button on the transmitter. States are
active-high.
4.3 Serial Number
Each Advanced KEELOQ encoder transmits its 32-bit
serial number with each transmission. It is intended
that this serial number be unique to a system. It is set
in the Serial Number Configuration registers, listed in
Table 3-7.
4.4 Seed Code Serial Number
The transmitter has the possibility to set the serial
number which will be transmitted with a seed
transmission. In a typical system, this serial number is
transmitted as 0xFFFFFFFF; however, the user can
configure this according to the actual application. The
seed code serial number is set in the Seed Code
Configuration registers, listed in Ta bl e 3 - 4 .
TABLE 4-1: ADVANCED KEELOQ®
BUTTON CODE
TRANSLATION
Button Function Code
SW0 xx1
SW1 x1x
SW2 1xx
MCS3122
DS40001762A-page 10 2014 Microchip Technology Inc.
4.5 Code Word Format
The Advanced KEELOQ code word is either 160 or
192-bit long. It comprises three sections (see Figure 4-1):
• 32 Bits of the Encoder’s Serial Number
• 128 Bits of the Encrypted Hopping Code
• 32 Bits of the Authorization Code (optional)
These segments are described in detail in the following
sections.
FIGURE 4-1: ADVANCED KEELOQ® CODE WORD FORMAT
4.5.1 FIXED CODE PORTION
The fixed code portion consists of 32 bits of the serial
number.
4.5.2 HOPPING CODE PORTION
The hopping code portion is calculated by encrypting
the synchronization counter and function code with the
encoder key. The hopping code is calculated when a
button press is registered.
4.5.3 AUTHORIZATION CODE PORTION
The authorization code is a cryptographically-strong
industry standard representation of the code word
suitable for authentication and integrity verification. It is
generated by using the on-board AES encryption
algorithm in CBC-MAC mode. The calculation takes
place over the entire code word, including the
encrypted and unencrypted portions, using the
authorization key as input. Figure 4-2 shows a
representation of how this calculation is performed.
This calculation is truncated to its Least Significant 32
bits for transmission.
The authorization code requires a shared secret called
the authorization key. This key is set in the
Authorization Key Configuration register, listed in
Table 3-6.
FI G U RE 4 - 2 : AUTHORIZATION CODE
CALCULATION
The authorization code portion consists of the 32-bit Least
Significant bits of the authorization code.
Serial Number 0x55AA55
32 bits
Fixed Portion 128 bits Encrypted Hopping Code
Authorization
Code
32 bits
Auth Portion
Sync.
Counter 0x55 Function
Code 0xAA55AA55 0xAA55 0xAA55
32-bits 24-bits 24-bits 8-bits 8-bits 32-bits 16-bits 16-bits 32-bits
Note: The data is sent LSB first (in this figure from right to left).
Serial Encrypted
0
Authorization
Key Authorization
Code
EE
Number Code Word
2014 Microchip Technology Inc. DS40001762A-page 11
MCS3122
4.5.4 SEED WORD FORMAT
The seed word is used when pairing the transmitter to
a receiver using a secure learn methodology. The seed
code word format is shown is Figure 4-3. While the
MCS3122 Flash data contains user-configurable 64-bit
seed data, the encoder will send 128-bit seed code.
The 128-bit seed code is constructed using the
user-configured seed code for the lower 64 bits of the
seed. The upper 64 bits are added by MCS3122 as 8
bytes with a 0x12 value.
FIGURE 4-3: ADVANCED KEELOQ® SEED WORD FORMAT(1)
Serial Number 64-Bit Padded Seed Upper Value(2) 64-Bit Configurable Seed Lower Value
32 bits
Fixed Portion 128 bit Seed
Authorization
Code
32 bits
Auth. Portion
Note 1: MCS3122 can set a different serial number for the seed packet. This is typically set to 0xFFFFFFFF.
2: The padded value is 0x1212121212121212.
3: The data is sent LSB first (in this figure from right to left.
MCS3122
DS40001762A-page 12 2014 Microchip Technology Inc.
5.0 TRANSMITTER OPERATION
5.1 Dat a Modulation Format and Baud
Rate
A transmission is made up of several code words. Each
code word contains a preamble, header and data. A
code word is separated from another code word by
guard time.
All timing specifications for the modulation formats are
based on a basic Time Element, described as TE. See
Section 5.2 “Baud Rate” for details on baud rate
calculation. This timing element can be set to a wide
range of values. The length of the preamble, header
and guard is fixed. The guard time is fixed to a typical
18.5 ms.
FIGURE 5-1: PWM TRANS MISSI ON FORMAT
FIGURE 5-2: MANCHESTER TRANSMISSION FORMAT
116
31 TEPreamble 10 TE
Header Encrypted Portion Fixed Code Portion Guard
Time
TETETE
TBP
Logic ‘0’
Logic ‘1’
116
Preamble Encrypted Portion Fixed Code Portion Guard
Time
TETE
TBP
Logic ‘0’
Logic ‘1’
2
10 TE
Header
bit 1bit 0 bit 2Start bit
Stop bit
2014 Microchip Technology Inc. DS40001762A-page 13
MCS3122
5.2 Baud Rate
The baud rate of an encoder’s transmission is highly
configurable using the two bits in the Transmitter
Setting Byte 1 register (0x35).
5.3 Transmission Modulation Format
The RF transmission can be configured to modulate
using Frequency-Shift Keying (FSK) or On-Off Keying
(OOK). The selection is done using one bit in the
Transmitter Settings Byte 0 register (0x34).
5.4 Frequency and Band Selection
The RF frequency configuration is performed by
selecting the appropriate bits in the Transmitter
Settings Byte 0 register (0x34).
5.5 Deviation Selection
When using FSK modulation, the frequency deviation
can be configured using bits <7:6> in the Transmitter
Settings Byte 0 register (0x34).
5.6 Power Output
The RF output power can be configured to either 0 dBm
or 10 dBm. The setting is done using bit <5> in the
Transmitter Settings Byte 0 register (0x34).
TABLE 5-1: BAUD RATE SELECTION
OPTIONS
TE (µS) Bits <5:4>
200 1:1
150 1:4
100 1:4
50 1:16
TABLE 5-2: MODULATION FORMAT
SELECTION OPTIONS
Modulat ion Bit <3>
FSK 0
OOK 1
TABLE 5-3: FREQUENCY SELECTION
OPTIONS
Frequency Bits <2:0>
315.00 MHz(1) 000
390.00 MHz 001
418.00 MHz 010
433.92 MHz 011
868.30 MHz 100
868.65 MHz 101
868.90 MHz 110
915.00 MHz 111
Note 1: For 315.00 MHz operation, a 24 MHz
crystal is required. All the other frequency
settings will require a 26 MHz crystal.
TABLE 5-4: FREQUENCY DEVIATION
SELECTION OPTIONS
Deviation Bit s <7:6 >
200 kHz 11
100 kHz 10
75 kHz 01
50 kHz 00
TABLE 5-5: OUTPUT POWER SELECTION
OPTIONS
Out Power Bit <5>
0 dBm 0
10 dBm 1
MCS3122
DS40001762A-page 14 2014 Microchip Technology Inc.
5.7 Crystal Selection
Once the frequency band has been selected, the choice
of crystal frequency is flexible provided the crystal
meets the specifications summarized in Table 5-6, the
boundaries of the Encoder Frequency Configuration
value are followed and the RF transmit frequency error
is acceptable to the system design.
5.8 Seed Button Configuration
The MCS3122 allows the user to select which button
combination will output the seed transmission instead
of the normal data packet. Tabl e 5 -7 lists all the
possible button combinations.
5.9 Code Word Complet ion
MCS3122 always ensures that a full and complete
code word is transmitted even if all buttons are
released before transmission is complete.
5.10 Maximum Code Words
This feature sets a maximum number of code words
transmitted by a button configuration. If a button is kept
pressed, the maximum allowed code words will be
transmitted. If a new button is pressed or a new button
press combination is used, the process will be restarted
and the maximum number of words will be transmitted.
TABLE 5-6: CRYSTAL RESONATOR SPECIFICATIONS
Symbol Description Min. Typ. Max. Unit
fREF Crystal Frequency — 26 or 24(1) —MHz
CLLoad Capacitance — 15 — pF
ESR Equivalent Series Resistance — — 100 Ω
Note 1: When selecting the 315.000 MHz frequency, a 24 MHz crystal is required.
TABLE 5-7: SEED BUTTON
CONFIGURATION OPTIONS
SW2 SW1 SW0 Bit Settings
<3> and
<1:0>
Closed Closed Closed 000
Closed Closed Open 001
Closed Open Closed 010
Closed Open Open 011
Open Closed Closed 100
Open Closed Open 101
Open Open Closed 110
Open Open Open 111(1)
Note 1: The button combination corresponding to
the setting ‘111’ will not generate a seed
combination since it corresponds to all
buttons not pressed. Setting the bits to
this value will disable the seed packet
sending (i.e., no button combination will
send a seed code).
2014 Microchip Technology Inc. DS40001762A-page 15
MCS3122
6.0 INTEGRATING MC S3122 INTO
A SYSTEM
FIGU RE 6-1 : TYPICA L D ECO D ER
OPERATION
6.1 Decoder Operation
The decoder waits until a transmission is received. The
received serial number is compared to the EEPROM
table of learned transmitters to first determine if this
transmitter’s use is allowed in the system. If from a
paired transmitter, the transmission is decrypted using
the stored crypt key and authenticated via the
Discrimination bits for appropriate crypt key usage. If
the decryption is valid, the synchronization value is
evaluated (see Figure 6-1).
6.2 Synchronization with a Decoder
The KEELOQ technology includes a sophisticated
synchronization technique that does not require the
calculation and storage of future codes. The technique
securely blocks invalid transmission while providing
transparent resynchronization to transmitters
inadvertently activated away from the receiver.
Figure 6-2 shows a three-partition, rotating
Synchronization window. The size of each window is
optional but the technique is fundamental. Each time a
transmission is authenticated, the intended function is
executed and the transmission’s synchronization
counter value is stored in EEPROM. From the currently
stored counter value there is an initial Single Operation
Forward window of 16 codes. If the difference between
a received synchronization counter and the last stored
counter is within 16, the intended function will be
executed on a single button press and the new
synchronization counter will be stored. Storing the new
synchronization counter value effectively rotates the
entire Synchronization window.
A Double Operation (Resynchronization) window
further exists from the Single Operation window up to
8M code forward of the currently stored counter value.
It is referred to as Double Operation because a
transmission with a synchronization counter in this
window will require an additional, sequential counter
transmission prior to executing the intended function.
Upon receiving the sequential transmission the
decoder executes the intended function and stores the
synchronization counter value. This resynchronization
occurs transparently to the user, as it is human nature
to press the button a second time if the first was
unsuccessful.
The third window is a Blocked window ranging from the
Double Operation window to the currently stored
synchronization counter value. Any transmission with
synchronization counter value within this window will
be ignored. This window excludes previously used
code-grabbed transmissions from accessing the
system.
Rev. 20-000013A
1/29/2014
Start
Does
Serial
Number
Match?
Transmission
Received?
Is Counter
Within 16?
Is Counter
Within 32K?
Decrypt Transmission
Is
Decryption
Valid?
Save Counter in
Temporary Location
Execute
Command and
Update Counter
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
Note: The synchronization method described in
this section is an exemplar method. It may
be altered to fit the needs and capabilities
of a particular system.
MCS3122
DS40001762A-page 16 2014 Microchip Technology Inc.
FIGURE 6-2: SYNCHRONIZATION WINDOW
6.3 Security Considerations
The strength of this security is based on keeping a
secret inside the transmitter that can be verified by
encrypted transmissions to a trained receiver. The
transmitter’s secret is the manufacturer’s key, not the
encryption algorithm. If that key is compromised, then
a smart transceiver can capture any serial number,
create a valid code word and trick all receivers trained
with that serial number. The key cannot be read from
the EEPROM without costly die probing, but it can be
calculated by brute force decryption attacks on
transmitted code words. The cost for these attacks
should exceed what the manufacturer would want to
protect.
To protect the security of other receivers with the same
manufacturer’s code, the manufacturer should use the
random seed for secure learn. It is a second secret that
is unique for each transmitter. If a manufacturer’s key is
compromised, clone transmitters can be created, but
without the unique seed, they have to be relearned by
the receiver. In the same way, if the transmissions are
decrypted by brute force on a computer, the random
seed hides the manufacturer’s key and prevents more
than one transmitter from being compromised.
The length of the code word at these baud rates make
brute force attacks that guess the hopping code take
years. To make the receiver less susceptible to this
attack, it should test all bits in the decrypted code for
the correct value, not just the low counter bits and
function code.
The main benefit of hopping codes is to prevent the
retransmission of captured code words. This works
very well for code words which the receiver decodes.
Its weakness is that, if a code is captured when the
receiver misses it, the code may trick the receiver once
if it is used before the next valid transmission. The
receiver should increment the counter on questionable
code word receptions. The transmitter should use
separate buttons for lock and unlock functions. A
different method would be to require two different
buttons in sequence to gain access.
There are more ways to make KEELOQ systems more
secure, but they all have trade-offs. The user should
find a balance between security, design effort and
usability, particularly in failure modes. For example, if a
button sticks or kids play with it, the counter should not
advance into the Blocked Code window, rendering the
transmitter useless or requiring retraining.
Blocked
Window
(8M Codes)
Double Operation
(Resynchronization
Window)
(8M Codes)
Stored
Synchronization
Counter Value
Single Operation
Window
(16 Codes)
Entire window rotates
to eliminate use of
previously used codes
2014 Microchip Technology Inc. DS40001762A-page 17
MCS3122
7.0 ELECTRICAL SPECIFICATIONS
7.1 Absolute Maximum Ratings(†)
Ambient temperature under bias........................................................................................................ -40°C to +85°C
Storage temperature ........................................................................................................................ -55°C to +150°C
Voltage on pins with respect to VSS
on VDD pin ............................................................................................................................................. 0-3.9V
on all other pins ............................................................................................................ -0.3V to (VDD + 0.3V)
Maximum current
on any output pin ................................................................................................................................ 25 mA
7.2 Standard Operati ng Conditions
The standard operating conditions for any device are defined as:
Operating Voltage: VDDMIN VDD VDDMAX
Operating Temperature: TA_MIN TA TA_MAX
VDD — Operating Supply Voltage
VDDMIN ................................................................................................................................................... +2.0V
VDDMAX .................................................................................................................................................. +3.7V
TA — Operating Ambient Temperature Range
T
A_MIN .................................................................................................................................................... -40°C
T
A_MAX................................................................................................................................................... +85°C
IDD — Supply Current
At 315 MHz, +10 dBm, FSK, typical(1) ................................................................................................ +15 mA
At 315 MHz, +10 dBm, OOK, typical(1) ............................................................................................... +11 mA
At 315 MHz, +0 dBm, FSK, typical(1) .................................................................................................... +9 mA
At 915 MHz, +10 dBm, FSK, typical(1) ............................................................................................. +17.5 mA
At 915 MHz, +0 dBm, FSK, typical(1) ............................................................................................... +10.5 mA
IPD — Standby Current
VDD = 3V, typical(1)............................................................................................................................ +0.23 µA
VIH — Input High Voltage, minimum.............................................................................................. 0.25 VDD + 0.8V
VIL — Input Low Voltage, maximum.......................................................................................................... 0.15 VDD
VOH — Output High Voltage
IOH = 3 mA, VDD = 3.3V, minimum..................................................................................................VDD – 0.7V
VOL — Output Low Voltage
IOL = 6 mA, VDD = 3.3V, maximum ......................................................................................................... +0.6V
ILED — LED Sink Current, maximum.......................................................................................................... +25 mA
† NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at those or any other conditions above those
indicated in the operation listings of this specification is not implied. Exposure above maximum rating conditions for
extended periods may affect device reliability.
Note 1: Typical values are at 25°C.
MCS3122
DS40001762A-page 18 2014 Microchip Technology Inc.
8.0 PACKAGING INFORMATION
8.1 Package Marking Information
*Standard PIC® device marking consists of Microchip part number, year code, week code, and traceability
code. For PIC device marking beyond this, certain price adders apply. Please check with your Microchip
Sales Office. For QTP devices, any special marking adders are included in QTP price.
14-Lead TSSOP (4.4 mm) Example
YYWW
NNN
XXXXXXXX
MCS3122
1409
017
Legend: XX...X Customer-specific information
Y Year code (last digit of calendar year)
YY Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanumeric traceability code
Pb-free JEDEC® designator for Matte Tin (Sn)
*This package is Pb-free. The Pb-free JEDEC designator ( )
can be found on the outer packaging for this package.
Note: In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line, thus limiting the number of available
characters for customer-specific information.
3
e
3
e
2014 Microchip Technology Inc. DS40001762A-page 19
MCS3122
8.2 Package Details
The following sections give the technical details of the packages.
Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
MCS3122
DS40001762A-page 20 2014 Microchip Technology Inc.
Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
2014 Microchip Technology Inc. DS40001762A-page 21
MCS3122
Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
MCS3122
DS40001762A-page 22 2014 Microchip Technology Inc.
APPENDIX A: REVISION HISTORY
Revision A (October 2014)
Initial release of this document.
2014 Microchip Technology Inc. DS40001762A-page 23
MCS3122
THE MICROCHIP WEB SITE
Microchip provides online support via our WWW site at
www.microchip.com. This web site is used as a means
to make files and information easily available to
customers. Accessible by using your favorite Internet
browser, the web site contains the following
information:
•Product Support – Data sheets and errata,
application notes and sample programs, design
resources, user’s guides and hardware support
documents, latest software releases and archived
software
•General Technical Support – Frequently Asked
Questions (FAQ), technical support requests,
online discussion groups, Microchip consultant
program member listing
•Business of Microchip – Product selector and
ordering guides, latest Microchip press releases,
listing of seminars and events, listings of
Microchip sales offices, distributors and factory
representatives
CUSTOMER CHANGE NOTIFICATION
SERVICE
Microchip’s customer notification service helps keep
customers current on Microchip products. Subscribers
will receive e-mail notification whenever there are
changes, updates, revisions or errata related to a
specified product family or development tool of interest.
To register, access the Microchip web site at
www.microchip.com. Under “Support”, click on
“Customer Change Notification” and follow the
registration instructions.
CUSTOMER SUPP ORT
Users of Microchip products can receive assistance
through several channels:
• Distributor or Representative
• Local Sales Office
• Field Application Engineer (FAE)
• Technical Support
Customers should contact their distributor,
representative or Field Application Engineer (FAE) for
support. Local sales offices are also available to help
customers. A listing of sales offices and locations is
included in the back of this document.
Technical support is a vailable through the web si te
at: http://microchip.com/support.
MCS3122
DS40001762A-page 24 2014 Microchip Technology Inc.
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO. X/XX XXX
PatternPackageTemperature
Range
Device
Device: MCS3122
Tape and Reel
Option: Blank = Standard packaging (tube or tray)
T = Tape and Reel(1)
Temperature
Range: I= -40C to +85C (Industrial)
Package:(2) ST = TSSOP
Pattern: QTP, SQTP, Code or Special Requirements
(blank otherwise)
Examples:
a) MCS3122 - I/ST
Industrial temperature,
TSSOP package
Note 1: Tape and Reel identifier only appears in the
catalog part number description. This
identifier is used for ordering purposes and is
not printed on the device package. Check
with your Microchip Sales Office for package
availability with the Tape and Reel option.
2: For other small form-factor package
availability and marking information, please
visit www.microchip.com/packaging or
contact your local sales office.
[X](1)
Tape and Reel
Option
-
2014 Microchip Technology Inc. DS40001762A-page 25
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR
FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip
devices in life support and/or safety applications is entirely at
the buyer’s risk, and the buyer agrees to defend, indemnify and
hold harmless Microchip from any and all damages, claims,
suits, or expenses resulting from such use. No licenses are
conveyed, implicitly or otherwise, under any Microchip
intellectual property rights.
Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
FlashFlex, flexPWR, JukeBlox, KEELOQ, KEELOQ logo, Kleer,
LANCheck, MediaLB, MOST, MOST logo, MPLAB,
OptoLyzer, PIC, PICSTART, PIC32 logo, RightTouch, SpyNIC,
SST, SST Logo, SuperFlash and UNI/O are registered
trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
The Embedded Control Solutions Company and mTouch are
registered trademarks of Microchip Technology Incorporated
in the U.S.A.
Analog-for-the-Digital Age, BodyCom, chipKIT, chipKIT logo,
CodeGuard, dsPICDEM, dsPICDEM.net, ECAN, In-Circuit
Serial Programming, ICSP, Inter-Chip Connectivity, KleerNet,
KleerNet logo, MiWi, MPASM, MPF, MPLAB Certified logo,
MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code
Generation, PICDEM, PICDEM.net, PICkit, PICtail,
RightTouch logo, REAL ICE, SQI, Serial Quad I/O, Total
Endurance, TSHARC, USBCheck, VariSense, ViewSpan,
WiperLock, Wireless DNA, and ZENA are trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
Silicon Storage Technology is a registered trademark of
Microchip Technology Inc. in other countries.
GestIC is a registered trademarks of Microchip Technology
Germany II GmbH & Co. KG, a subsidiary of Microchip
Technology Inc., in other countries.
All other trademarks mentioned herein are property of their
respective companies.
© 2014, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
ISBN: 978-1-63276-724-0
Note the following details of the code protection feature on Microchip devices:
• Microchip products meet the specification contained in their particular Microchip Data Sheet.
• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperiph erals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
QUALITY MANAGEMENT S
YSTEM
CERTIFIED BY DNV
== ISO/TS 16949 ==
DS40001762A-page 26 2014 Microchip Technology Inc.
AMERICAS
Corporate Office
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Tel: 480-792-7200
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Tel: 60-4-227-8870
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Tel: 65-6334-8870
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Worldwide Sales and Service
03/25/14
