In-System Reprogrammable Flash Program Memory

The ATtiny4/5/9/10 contains 512/1024 bytes On-chip In-System Reprogrammable Flash memory for program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as 256/512 x 16.

The Flash memory has an endurance of at least 10,000 write/erase cycles. The device Program Counter (PC) is 9 bits wide, thus addressing the 256/512 program memory locations, starting at 0x000. Memory Programming contains a detailed description on Flash data serial downloading.

Constant tables can be allocated within the entire address space of program memory by using load/store instructions. Since program memory can not be accessed directly, it has been mapped to the data memory. The mapped program memory begins at byte address 0x4000 in data memory. Although programs are executed starting from address 0x000 in program memory it must be addressed starting from 0x4000 when accessed via the data memory.

Internal write operations to Flash program memory have been disabled and program memory therefore appears to firmware as read-only. Flash memory can still be written to externally but internal write operations to the program memory area will not be successful.

Timing diagrams of instruction fetch and execution are presented in Instruction Execution Timing section.