Atmel AVR ATtiny15L User manual

1
Features
•High-performance, Low-power AVR®8-bit Microcontroller
•Advanced RISC Architecture
– 90 Powerful Instructions – Most Single Clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
•Non-volatile Program and Data Memories
– 1K Byte In-System Programmable Flash Program Memory
Endurance: 1,000 Write/Erase Cycles
– 64 Bytes EEPROM
Endurance: 100,000 Write/Erase Cycles
– Programming Lock for Flash Program Data Security
•Peripheral Features
– Interrupt and Wake-up on Pin Change
– Two 8-bit Timer/Counters with Separate Prescalers
– One 150 kHz, 8-bit High-speed PWM Output
– 4-channel 10-bit ADC
One Differential Voltage Input with Optional Gain of 20x
– On-chip Analog Comparator
– Programmable Watchdog Timer with On-chip Oscillator
•Special Microcontroller Features
– In-System Programmable via SPI Port
– Enhanced Power-on Reset Circuit
– Programmable Brown-out Detection Circuit
– Internal, Calibrated 1.6 MHz Tunable Oscillator
– Internal 25.6 MHz Clock Generator for Timer/Counter
– External and Internal Interrupt Sources
– Low-power Idle and Power-down Modes
•Power Consumption at 1.6 MHz, 3V, 25°C
– Active: 3.0 mA
– Idle Mode: 1.0 mA
– Power-down: < 1 µA
•I/O and Packages
– 8-lead PDIP and 8-lead SOIC: 6 Programmable I/O Lines
•Operating Voltages
– 2.7V - 5.5V
•Internal 1.6 MHz System Clock
Pin Configuration
1
2
3
4
8
7
6
5
(
RESET/ADC0) PB5
(ADC3) PB4
(ADC2) PB3
GND
VCC
PB2 (ADC1/SCK/T0/INT
0)
PB1 (AIN1/MISO/OC1A)
PB0 (AIN0/AREF/MOSI)
PDIP/SOIC
8-bit
Microcontroller
with 1K Byte
Flash
ATtiny15L
Not recommended for new
design
Rev. 1187H–AVR–09/07

2ATtiny15L 1187H–AVR–09/07
Description The ATtiny15L is a low-power CMOS 8-bit microcontroller based on the AVR RISC
architecture. By executing powerful instructions in a single clock cycle, the ATtiny15L
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 connected to the Arithmetic Logic Unit (ALU), allowing
two independent registers to be accessed in one single instruction executed in one clock
cycle. The resulting architecture is more code efficient while achieving throughputs up to
ten times faster than conventional CISC microcontrollers.
The ATtiny15L provides 1K byte of Flash, 64 bytes EEPROM, six general purpose I/O
lines, 32 general purpose working registers, two 8-bit Timer/Counters, one with high-
speed PWM output, internal Oscillators, internal and external interrupts, programmable
Watchdog Timer, 4-channel 10-bit Analog-to-Digital Converter with one differential volt-
age input with optional 20x gain, and three software-selectable Power-saving modes.
The Idle mode stops the CPU while allowing the ADC, anAlog Comparator,
Timer/Counters and interrupt system to continue functioning. The ADC Noise Reduction
mode facilitates high-accuracy ADC measurements by stopping the CPU while allowing
the ADC to continue functioning. The Power-down mode saves the register contents but
freezes the Oscillators, disabling all other chip functions until the next interrupt or Hard-
ware Reset. The wake-up or interrupt on pin change features enable the ATtiny15L to
be highly responsive to external events, still featuring the lowest power consumption
while in the Power-saving modes.
The device is manufactured using Atmel’s high-density, Non-volatile memory technol-
ogy. By combining a RISC 8-bit CPU with Flash on a monolithic chip, the ATtiny15L is a
powerful microcontroller that provides a highly flexible and cost-efficient solution to
many embedded control applications. The peripheral features make the ATtiny15L par-
ticularly suited for battery chargers, lighting ballasts and all kinds of intelligent sensor
applications.
The ATtiny15L AVR is supported with a full suite of program and system development
tools including macro assemblers, program debugger/simulators, In-circuit emulators
and evaluation kits.

3
ATtiny15L
1187H–AVR–09/07
Block Diagram Figure 1. The ATtiny15L Block Diagram
PROGRAM
COUNTER
INTERNAL
OSCILLATOR
WATCHDOG
TIMER
STACK
POINTER
PROGRAM
FLASH
HARDWARE
STACK
MCU CONTROL
REGISTER
GENERAL
PURPOSE
REGISTERS
INSTRUCTION
REGISTER
TIMER/
COUNTER0
INSTRUCTION
DECODER
DATA DIR.
REG.PORT B
DATA REGISTER
PORT B
PROGRAMMING
LOGIC
TIMING AND
CONTROL
TIMER/
COUNTER1
MCU STATUS
REGISTER
STATUS
REGISTER
ALU
PORT B DRIVERS
PB0-PB5
VCC
GND
CONTROL
LINES
+
-
ANALOG
COMPARATOR
8-BIT DATA BUS
Z
ISP MODULE
INTERRUPT
UNIT
DATA
EEPROM
INTERNAL
OSCILLATOR
TUNABLE
ANALOG MUX ADC

4ATtiny15L 1187H–AVR–09/07
Pin Descriptions
VCC Supply voltage pin.
GND Ground pin.
Port B (PB5..PB0) Port B is a 6-bit I/O port. PB4..0 are I/O pins that can provide internal pull-ups (selected
for each bit). PB5 is input or open-drain output. The use of pin PB5 is defined by a fuse
and the special function associated with this pin is External Reset. The port pins are tri-
stated when a reset condition becomes active, even if the clock is not running.
Port B also accommodates analog I/O pins. The Port B pins with alternate functions are
shown in Table 1.
Analog Pins Up to four analog inputs can be selected as inputs to Analog-to-Digital Converter (ADC).
Internal Oscillators The internal Oscillator provides a clock rate of nominally 1.6 MHz for the system clock
(CK). Due to large initial variation (0.8 -1.6 MHz) of the internal Oscillator, a tuning capa-
bility is built in. Through an 8-bit control register – OSCCAL – the system clock rate can
be tuned with less than 1% steps of the nominal clock.
There is an internal PLL that provides a 16x clock rate locked to the system clock (CK)
for the use of the Peripheral Timer/Counter1. The nominal frequency of this peripheral
clock, PCK, is 25.6 MHz.
Table 1. Port B Alternate Functions
Port Pin Alternate Function
PB0 MOSI (Data Input Line for Memory Downloading)
AREF (ADC Voltage Reference)
AIN0 (Analog Comparator Positive Input)
PB1 MISO (Data Output Line for Memory Downloading)
OC1A (Timer/Counter PWM Output)
AIN1 (Analog Comparator Negative Input)
PB2 SCK (Serial Clock Input for Serial Programming)
INT0 (External Interrupt0 Input)
ADC1 (ADC Input Channel 1)
T0 (Timer/Counter0 External Counter Input)
PB3 ADC2 (ADC Input Channel 2)
PB4 ADC3 (ADC Input Channel 3)
PB5 RESET (External Reset Pin)
ADC0 (ADC Input Channel 0)

5
ATtiny15L
1187H–AVR–09/07
ATtiny15L
Architectural
Overview
The fast-access Register File concept contains 32 x 8-bit general purpose working reg-
isters with a single-clock-cycle access time. This means that during one single clock
cycle, one ALU (Arithmetic Logic Unit) operation is executed. Two operands are output
from the Register File, the operation is executed, and the result is stored back in the
Register File – in one clock cycle.
Two of the 32 registers can be used as a 16-bit pointer for indirect memory access. This
pointer is called the Z-pointer, and can address the Register File, IO file and the Flash
Program memory.
Figure 2. The ATtiny15L AVR RISC Architecture
The ALU supports arithmetic and logic functions between registers or between a con-
stant and a register. Single-register operations are also executed in the ALU. Figure 2
shows the ATtiny15L AVR RISC microcontroller architecture. The AVR uses a Harvard
architecture concept with separate memories and buses for program and data memo-
ries. The program memory is accessed with a two-stage pipeline. While one instruction
is being executed, the next instruction is pre-fetched from the program memory. This
concept enables instructions to be executed in every clock cycle. The Program memory
is In-System Programmable Flash memory.
With the relative jump and relative call instructions, the whole address space is directly
accessed. All AVR instructions have a single 16-bit word format, meaning that every
program memory address contains a single 16-bit instruction.
During interrupts and subroutine calls, the return address Program Counter (PC) is
stored on the Stack. The Stack is a 3-level-deep Hardware Stack dedicated for subrou-
tines and interrupts.
The I/O memory space contains 64 addresses for CPU peripheral functions as Control
Registers, Timer/Counters and other I/O functions. The memory spaces in the AVR
architecture are all linear and regular memory maps.
512 x 16
Program
FLASH
Instruction
Register
Instruction
Decoder
Program
Counter
Control Lines
32 x 8
General
Purpose
Registrers
ALU
Direct Addressing
Status
and Test
Control
Registrers
Interrupt
Unit
2 x 8-bit
Timer/Counter
Watchdog
Timer
Analog
Comparator
I/O Lines
Data Bus 8-bit
SPI Unit
ADC
64 x 8
EEPROM

6ATtiny15L 1187H–AVR–09/07
A flexible interrupt module has its control registers in the I/O space with an additional
Global Interrupt Enable bit in the Status Register. All the different interrupts have a sep-
arate Interrupt Vector in the Interrupt Vector table at the beginning of the program
memory. The different interrupts have priority in accordance with their Interrupt Vector
position. The lower the Interrupt Vector address, the higher the priority.
The General Purpose
Register File Figure 3 shows the structure of the 32 general purpose registers in the CPU.
Figure 3. AVR CPU General Purpose Working Registers
All the register operating instructions in the instruction set have direct- and single-cycle
access to all registers. The only exception is the five constant arithmetic and logic
instructions SBCI, SUBI, CPI, ANDI, and ORI between a constant and a register and the
LDI instruction for load-immediate constant data. These instructions apply to the second
half of the registers in the Register File – R16..R31. The general SBC, SUB, CP, AND,
OR, and all other operations between two registers or on a single-register apply to the
entire Register File.
Registers 30 and 31 form a 16-bit pointer (the Z-pointer) which is used for indirect Flash
memory and Register File access. When the Register File is accessed, the contents of
R31 is discarded by the CPU.
The ALU – Arithmetic
Logic Unit The high-performance AVR ALU operates in direct connection with all the 32 general
purpose working registers. Within a single clock cycle, ALU operations between regis-
ters in the Register File are executed. The ALU operations are divided into three main
categories – arithmetic, logic and bit-functions. Some microcontrollers in the AVR prod-
uct family feature a hardware multiplier in the arithmetic part of the ALU.
The Flash Program
Memory The ATtiny15L contains 1K byte On-chip, In-System Programmable Flash memory for
program storage. Since all instructions are single 16-bit words, the Flash is organized as
512 x 16 words. The Flash memory has an endurance of at least 1,000 write/erase
cycles.
The ATtiny15L Program Counter is nine bits wide, thus addressing the 512 words Flash
Program memory.
See page 54 for a detailed description on Flash memory programming.
70
R0
R1
R2
General …
Purpose …
Working R28
Registers R29
R30 (Z-register Low Byte)R3
R31 (Z-register High Byte)

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ATtiny15L
1187H–AVR–09/07
The Program and Data
Addressing Modes The ATtiny15L AVR RISC Microcontroller supports powerful and efficient addressing
modes. This section describes the various addressing modes supported in the
ATtiny15L. In the figures, OP means the operation code part of the instruction word. To
simplify, not all figures show the exact location of the addressing bits.
Register Direct, Single-
register Rd Figure 4. Direct Single-register Addressing
The operand is contained in register d (Rd).
Register Indirect Figure 5. Indirect Register Addressing
The register accessed is the one pointed to by the Z-register low byte (R30).
Register Direct, Two Registers
Rd and Rr Figure 6. Direct Register Addressing, Two Registers
REGISTER FILE
0
31
3
0
Z-register

8ATtiny15L 1187H–AVR–09/07
Operands are contained in register r (Rr) and d (Rd). The result is stored in register d
(Rd).
I/O Direct Figure 7. I/O Direct Addressing
Operand address is contained in 6 bits of the instruction word. “n” is the destination or
source register address.
Relative Program Addressing,
RJMP and RCALL Figure 8. Relative Program Memory Addressing
Program execution continues at address PC + k + 1. The relative address k is -2048 to
2047.
Constant Addressing using
the LPM Instruction Figure 9. Code Memory Constant Addressing
+1
$1FF

9
ATtiny15L
1187H–AVR–09/07
Constant byte address is specified by the Z-register contents. The 15 MSBs select word
address (0 - 511), and LSB selects low byte if cleared (LSB = 0) or high byte if set
(LSB = 1).
Subroutine and Interrupt
Hardware Stack The ATtiny15L uses a 3-level-deep Hardware Stack for subroutines and interrupts. The
Hardware Stack is nine bits wide and stores the Program Counter (PC) return address
while subroutines and interrupts are executed.
RCALL instructions and interrupts push the PC return address onto Stack level 0, and
the data in the other Stack levels 1 - 2 are pushed one level deeper in the Stack. When
a RET or RETI instruction is executed the returning PC is fetched from Stack level 0,
and the data in the other Stack levels 1 - 2 are popped one level in the Stack.
If more than three subsequent subroutine calls or interrupts are executed, the first val-
ues written to the Stack are overwritten. Pushing four return addresses A1, A2, A3, and
A4 followed by four subroutine or interrupt returns, will pop A4, A3, A2, and once more
A2 from the Hardware Stack.
The EEPROM Data
Memory The ATtiny15L contains 64 bytes of data EEPROM memory. It is organized as a sepa-
rate data space, in which single bytes can be read and written. The EEPROM has an
endurance of at least 100,000 write/erase cycles. The access between the EEPROM
and the CPU is described on page 36, specifying the EEPROM Address Register, the
EEPROM Data Register, and the EEPROM Control Register.
Memory Access and
Instruction Execution Timing This section describes the general access timing concepts for instruction execution and internal memory access.
The AVR CPU is driven by the System Clock Ø, directly generated from the external
clock crystal for the chip. No internal clock division is used.
Figure 10 shows the parallel instruction fetches and instruction executions enabled by
the Harvard architecture and the fast-access Register File concept. This is the basic
pipelining concept to obtain up to 1 MIPS per MHz with the corresponding unique results
for functions per cost, functions per clocks, and functions per power-unit.
Figure 10. The Parallel Instruction Fetches and Instruction Executions
Figure 11 shows the internal timing concept for the Register File. In a single clock cycle
an ALU operation using two register operands is executed, and the result is stored back
to the destination register.
System Clock Ø
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2
nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
T1 T2 T3 T4

10 ATtiny15L 1187H–AVR–09/07
Figure 11. Single Cycle ALU Operation
I/O Memory The I/O space definition of the ATtiny15L is shown in Table 2.
System Clock Ø
Total Execution Time
R
egister Operands Fetch
ALU Operation Execute
Result Write Back
T1 T2 T3 T4
Table 2. ATtiny15L I/O Space(1)
Address Hex Name Function
$3F SREG Status Register
$3B GIMSK General Interrupt Mask Register
$3A GIFR General Interrupt Flag Register
$39 TIMSK Timer/Counter Interrupt Mask Register
$38 TIFR Timer/Counter Interrupt Flag Register
$35 MCUCR MCU Control Register
$34 MCUSR MCU Status Register
$33 TCCR0 Timer/Counter0 Control Register
$32 TCNT0 Timer/Counter0 (8-bit)
$31 OSCCAL Oscillator Calibration Register
$30 TCCR1 Timer/Counter1 Control Register
$2F TCNT1 Timer/Counter1 (8-bit)
$2E OCR1A Timer/Counter1 Output Compare Register A
$2D OCR1B Timer/Counter1 Output Compare Register B
$2C SFIOR Special Function I/O Register
$21 WDTCR Watchdog Timer Control Register
$1E EEAR EEPROM Address Register
$1D EEDR EEPROM Data Register
$1C EECR EEPROM Control Register
$18 PORTB Data Register, Port B
$17 DDRB Data Direction Register, Port B
$16 PINB Input Pins, Port B
$08 ACSR Analog Comparator Control and Status Register
$07 ADMUX ADC Multiplexer Select Register