Program memory
Flash, with the boot section at its top. Addresses in bytes.
Boot section0xE000 – 0xFFFF8 KB
Flash0x0000 – 0xFFFF64 KB
ATmega640 memory map
Where everything sits, at its exact address. The ATmega640 keeps program and data apart (Harvard): flash is read in words by the CPU, while registers, I/O and SRAM share one data address space.
Data memory
Working registers, I/O registers and SRAM in one space.
External RAM0x2200 – 0xFFFF55.5 KB
SRAM0x0200 – 0x21FF8 KB
I/O registers0x0020 – 0x01FF480 B
Working registers R0–R310x0000 – 0x001F32 B
EEPROM
Non-volatile data, kept without power.
EEPROM0x0000 – 0x0FFF4 KB
Every segment
| Segment | Space | Start | End | Size | Page |
|---|---|---|---|---|---|
| Working registers R0–R31 | data | 0x0000 | 0x001F | 32 B | |
| I/O registers | data | 0x0020 | 0x01FF | 480 B | |
| SRAM | data | 0x0200 | 0x21FF | 8 KB | |
| External RAM | data | 0x2200 | 0xFFFF | 55.5 KB | |
| EEPROM | eeprom | 0x0000 | 0x0FFF | 4 KB | 8 B |
| FUSES | fuses | 0x0000 | 0x0002 | 3 B | |
| LOCKBITS | lockbits | 0x0000 | 0x0000 | 1 B | |
| OSCCAL | osccal | 0x0000 | 0x0000 | 1 B | |
| Flash | prog | 0x0000 | 0xFFFF | 64 KB | 256 B |
| Boot section | prog | 0xE000 | 0xFFFF | 8 KB | 256 B |
| Boot section | prog | 0xF000 | 0xFFFF | 4 KB | 256 B |
| Boot section | prog | 0xF800 | 0xFFFF | 2 KB | 256 B |
| Boot section | prog | 0xFC00 | 0xFFFF | 1 KB | 256 B |
| SIGNATURES | signatures | 0x0000 | 0x0002 | 3 B |