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Im learning the debug progress to access memory system in a mcu
now i know how to read/write a register with a specific address
：write TAR and DRW in the AHB-AP
but how does AHB-AP read/write a core register like pc or sp which have no address
Take a look at the debug system registers in the ARMv7-M or ARMv8-M Architecture Reference Manual.
DCRSR (Debug Core Register Selector Register)
DCRDR (Debug Core Register Data Register)
Basically you select the register and operation (read/write) and start the transfer by writing to DCRSR. DCRDR holds the data to write or data read.