debugWIRE memtypes

Used for writing FLASH before a debug session, and reading FLASH during a debug session

Only FULL PAGE access is allowed

If the number of bytes requested does not match the flash page size, an error is returned ¹.

Software breakpoints are NOT filtered out

Used to read the device signature stored in the debugWIRE module itself

This signature may differ from the signature stored in FLASH and accessed through SPI programming interface

A read MUST be for exactly 3 bytes from address 0x00

Violating this will results in an error ²³

Byte 2 will always read 0x1E

Accesses SRAM and IO space during debugging

If used in programming mode, an error is returned ⁴

If a read attempts to read an area containing the OCDR register, an error is returned ⁵

A masked read must be used in this case

Any number of bytes (within payload restrictions) can be written or read in one operation

Used to read and write EEPROM during a debug session

Any number of bytes can be written or read in one operation

Uses monitor code heavily - may take some time to complete, depending proportionally upon the number of bytes being accessed

Used to access small amounts of FLASH during a debug session

If an odd number of bytes is requested, an error is returned ⁶

This memtype is efficient for reading full pages, or single words from FLASH

Multiple word requests are inefficient and may take time to complete

Software breakpoints are filtered out