PB013505-0607 eZ80Acclaim!® Flash Microcontrollers
eZ80F91 MCU
Product Brief
3
Universal Asynchronous Receiver/Transmitter
Each of the two UART channels contains a
transmitter, a receiver, control logic/registers, and a
Baud Rate Generator (BRG).
•The BRG produces a lower-frequency bit clock
from the system clock. All standard baud rates
up to 115 Kbps (and higher) are supported.
•The UART module implements the logic
required to support asynchronous communica-
tions, hardware flow control, and 9-bit charac-
ter format. The module also contains separate
16-byte-deep transmit and receive FIFOs.
Inter-Integrated Circuit
The I2C channel contains control registers and a
clock rate generator. The I2C interface operates in
four modes: Master Transmit or Receive and Slave
Transmit or Receive. A standard and fast I2C speed
of 100 kbps and 400 kbps are supported.
Serial Peripheral Interface
The SPI channel contains control registers and a
clock rate generator. The SPI is a synchronous
serial interface allowing multiple SPI devices to be
interconnected. The SPI interface is configured to
function either as a master or a slave.
Programmable Reload Timers
The eZ80F91 MCU provides four independent
Programmable Reloadable Counter Timers (PRT)
to handle complex timing functions. Each timer is
a 16-bit downcounter and offers a 4-bit clock
prescaler with four selectable taps for CLK ÷ 4,
CLK ÷ 16, CLK ÷ 64 and CLK ÷ 256. The timers
operates in basic mode supporting SINGLE-PASS
or CONTINUOUS count. Additional features
include 4 input captures, 4 output compares,
2 external event counters, and 4 PWMs that can
operate independently or in unison. Any one of the
input capture pins can be programmed as master
PWM power-trip inputs.
Watchdog Timer
The WDT features four programmable time-out
periods. It operates either from the main system
clock, the on-chip 32 KHz oscillator (from the
RTC), or the internal RC oscillator. The time-out
action of the WDT is user-programmable for either
a hardware reset or a non-maskable interrupt to the
eZ80® CPU. The source of action taken after a
WDT time-out is indicated by a WDT status bit.
Real Time Clock
The RTC allows counting of seconds, minutes,
hours, day-of-the-week, day-of-the-month, month,
year, and century. Alarms and interrupts can be set
for seconds, minutes, hours, and day-of-the-week.
The RTC input is taken either from the on-chip
32 KHz oscillator or from a 50/60 Hz input. The
RTC operates from an isolated RTC_VDD pin to
allow constant operation from a battery.
Chip-Select/Wait State Generator and WAIT Pin
Four independent chip selects facilitate glueless
interface to system memory and external devices.
Each chip-select can be configured for up to 7 wait
states and supports either memory or I/O space.
Memory chip selects can be individually
programmed on a 64 KB boundary. I/O chip
selects can choose a 256 byte section of I/O space.
The WAIT input pin allows interface with slow
peripherals. It also supports Z80® , Intel®, and
Motorola® bus modes.
JTAG Interface
An IEEE 1149.1-compatible five-pin test access
port (TAP) is provided to interface with on-chip
test logic defined by IEEE standard. The TAP also
includes Boundary Scan functions and is used to
control on-chip emulation/debugging capabilities.
Some features include software break points,
64-word trace buffer, complex break points using
address and data masks, and cascadable triggers.
PLL and On-Chip Crystal Oscillator
The eZ80F91 MCU features a low-power,
programmable PLL that can be selected to generate
the system clock. Taking the input from the
on-chip crystal oscillator, the PLL generates
system clock speed up to 50 MHz from low-cost,
low-frequency external crystals in the range of
1 MHz to 10 MHz.