The ATmega64/128 have an external memory bus for interfacing with up to 64k of memory. There are two 8-bit timers, and
two 16-bit, as well as two USARTS. The ISP programming port on these parts is a "dedicated" SPI port for programming,
but it shares SCK with the other SPI port.
Power Supply vs. Maximum Frequency
The ATmega64/128 are specified at a power supply voltage of 4.5V to 5.5V, 16MHz maximum frequency. The -L parts are
rated 8MHz from 2.7V to 5.5V. The calculator below will help determine the frequency you can run with a given
power supply voltage.
Maximum Frequency Calculator for ATmega64/128
|I/O Pins ||53|
|ADC Channels ||8|
|RT Counter ||1|
|Timers (8-bit) ||2|
|Timers (16-bit) ||2|
|PWM (8-bit) ||2|
|PWM (16-bit) ||4|
|Price (1's) ||$12.10||$17.61|
|Power Consumption (approximate) ||2.0mA/MHz@5V|
|Maximum I/O Current (per pin) ||40mA|
|Maximum I/O Current (all ports) ||unspecified|
|Maximum I/O Current (total)||400mA (QFP/MLF)|
Link to ATmega64 datasheet from Atmel's website.
Link to ATmega128 datasheet from Atmel's website.
"Minimal" ATmega128 Schematic Diagram
This is a minimal ATmega128 circuit. A more complete system would have an external memory interface as well.