Datasheet

3
ATtiny40 [SUMMARY DATASHEET]
8263BS–AVR–01/2013
1.1 Pin Description
1.1.1 VCC
Supply voltage.
1.1.2 GND
Ground.
1.1.3
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 and provided the reset pin has not been disabled. The minimum pulse length is given in Table 20-4
on page 155. Shorter pulses are not guaranteed to generate a reset.
The reset pin can also be used as a (weak) I/O pin.
1.1.4 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 alternate functions as analog inputs for the ADC, analog comparator and pin change interrupt as
described in “Alternate Port Functions” on page 47.
1.1.5 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. 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.
The port also serves the functions of various special features of the ATtiny40, as listed on page 37.
1.1.6 Port C (PC5:PC0)
Port C is a 6-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output buf-
fers have symmetrical drive characteristics with both high sink and source capability except PC3 which has the
RESET
capability. To use pin PC3 as an I/O pin, instead of RESET pin, program (‘0’) RSTDISBL fuse. As inputs,
Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins
are tri-stated when a reset condition becomes active, even if the clock is not running.
Port C has alternate functions as analog inputs for the ADC, analog comparator and pin change interrupt as
described in “Alternate Port Functions” on page 47.
The port also serves the functions of various special features of the ATtiny40, as listed on page 37.
2. Overview
ATtiny40 is a low-power CMOS 8-bit microcontroller based on the compact AVR enhanced RISC architecture. By
executing powerful instructions in a single clock cycle, the ATtiny40 achieves throughputs approaching 1 MIPS per
MHz allowing the system designer to optimize power consumption versus processing speed.
Figure 2-1. Block Diagram
The AVR core combines a rich instruction set with 16 general purpose working registers and system registers. All
registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be