The ATmega64 provides the following features: 64K bytes of In-System Programmable
Flash with Read-While-Write capabilities, 2K bytes EEPROM, 4K bytes SRAM, 53 gen-
eral purpose I/O lines, 32 general purpose working registers, Real Time Counter (RTC),
four flexible Timer/Counters with compare modes and PWM, two USARTs, a byte ori-
ented Two-wire Serial Interface, an 8-channel, 10-bit ADC with optional differential input
stage with programmable gain, programmable Watchdog Timer with internal Oscillator,
an SPI serial port, IEEE std. 1149.1 compliant JTAG test interface, also used for
accessing the On-chip Debug system and programming, and six software selectable
power saving modes. The Idle mode stops the CPU while allowing the SRAM,
Timer/Counters, SPI port, and interrupt system to continue functioning. The Power-
down mode saves the register contents but freezes the Oscillator, disabling all other
chip functions until the next interrupt or Hardware Reset. In Power-save mode, the asyn-
chronous timer continues to run, allowing the user to maintain a timer base while the
rest of the device is sleeping. The ADC Noise Reduction mode stops the CPU and all
I/O modules except asynchronous timer and ADC, to minimize switching noise during
ADC conversions. In Standby mode, the crystal/resonator Oscillator is running while the
rest of the device is sleeping. This allows very fast start-up combined with low power
consumption. In Extended Standby mode, both the main Oscillator and the asynchro-
nous timer continue to run.