debugWIRE memtypes

Table 1. debugWIRE memtypes
ID	Prog access	Debug access	Usage/rules
MEMTYPE_FLASH_PAGE	-	RW	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
MEMTYPE_SIGNATURE	-	R	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 ² ³ Byte 2 will always read 0x1E
MEMTYPE_SRAM	-	RW	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
MEMTYPE_EEPROM	-	RW	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
MEMTYPE_SPM	-	R	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