Rainbow Electronics ATtiny28L - Manual (Page 2)

2
ATtiny28L/V
1062E–10/01
Description
The ATtiny28 is a low-power CMOS 8-bit microcontroller based on the AVR RISC archi-
tecture. By executing powerful instructions in a single clock cycle, the ATtiny28 achieves
throughputs approaching 1 MIPS per MHz, allowing the system designer to optimize
power consumption versus processing speed. The AVR core combines a rich instruction
set with 32 general-purpose working registers. All the 32 registers are directly con-
nected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be
accessed in one single instruction executed in one clock cycle. The resulting architec-
ture is more code efficient while achieving throughputs up to ten times faster than
conventional CISC microcontrollers.
Block Diagram Figure 1. The ATtiny28 Block Diagram
The ATtiny28 provides the following features: 2K bytes of Flash, 11 general-purpose I/O
lines, 8 input lines, a high-current LED driver, 32 general-purpose working registers, an
8-bit timer/counter, internal and external interrupts, programmable Watchdog Timer with
internal oscillator and 2 software-selectable power-saving modes. The Idle Mode stops
the CPU while allowing the timer/counter and interrupt system to continue functioning.
The Power-down mode saves the register contents but freezes the oscillator, disabling
all other chip functions until the next interrupt or hardware reset. The wake-up or inter-
PROGRAM
COUNTER
INTERNAL
OSCILLATOR
WATCHDOG
TIMER
STACK
POINTER
PROGRAM
FLASH
MCU CONTROL
REGISTER
GENERAL
PURPOSE
REGISTERS
INSTRUCTION
REGISTER
TIMER/
COUNTER
INSTRUCTION
DECODER
DATA REGISTER
PORTB
PROGRAMMING
LOGIC
TIMING AND
CONTROL
INTERRUPT
UNIT
STATUS
REGISTER
ALU
PORTB
VCC
GND
CONTROL
LINES
+ -
ANALOG
COMPARATOR
8-BIT DATA BUS
Z
OSCILLATOR
PORTD
DATA REGISTER
PORTA
PORTA
PORTA CONTROL
REGISTER
XTAL2 XTAL1
RESET
HARDWARE
STACK
DATA REGISTER
PORTD
DATA DIR
REG. PORTD
HARDWARE
MODULATOR
INTERNAL
CALIBRATED
OSCILLATOR