Datasheet
5
8006ES–AVR–09/06
ATtiny24/44/84
2.2 Pin Descriptions
2.2.1 VCC
Supply voltage.
2.2.2 GND
Ground.
2.2.3 Port B (PB3...PB0)
Port B is a 4-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port B output buffers have symmetrical drive characteristics with both high sink and source
capability except PB3 which has the RESET
capability. To use pin PB3 as an I/O pin, instead of
RESET pin, program (‘0’) RSTDISBL fuse. As inputs, Port B pins that are externally pulled low
will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a
reset condition becomes active, even if the clock is not running.
Port B also serves the functions of various special features of the ATtiny24/44/84 as listed on
Section 12.3 ”Alternate Port Functions” on page 61.
2.2.4 RESET
Reset input. A low level on this pin for longer than the minimum pulse length will generate a
reset, even if the clock is not running. The minimum pulse length is given in Table 22-3 on page
183. Shorter pulses are not guaranteed to generate a reset.
2.2.5 Port A (PA7...PA0)
Port A is a 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port A output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port A pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port A pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port A has an alternate functions as analog inputs for the ADC, analog comparator,
timer/counter, SPI and pin change interrupt as described in ”Alternate Port Functions” on page
61
3. Resources
A comprehensive set of development tools, drivers and application notes, and datasheets are
available for download on http://www.atmel.com/avr.
4. About Code Examples
This documentation contains simple code examples that briefly show how to use various parts of
the device. These code examples assume that the part specific header file is included before
compilation. Be aware that not all C compiler vendors include bit definitions in the header files
and interrupt handling in C is compiler dependent. Please confirm with the C compiler documen-
tation for more details.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI”
instructions must be replaced with instructions that allow access to extended I/O. Typically
“LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.