4

ATtiny15L

1187DS–12/01

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)