16.12.2.2 Operation From a Debug Adapter

Debug adapters should access the DSU registers in the external address range [0x0100 – 0x1FFF].

If DAL.CPU0 is equal to 0 or 3, accessing the first 0x100 bytes causes the DSU bus matrix to return an error to the DAP. See the following table for information.

Table 16-4. DAP MEM AP0 Transaction Authorizations and Error Response Types
DBG Connection	DAL.CPU0	DAP transaction allowed?
DBG Connection	DAL.CPU0	DSU internal address space	DSU external address space	Other
Cold-p	0,3	N (BE)	Y	N (BE)
Hot-p	0,3	N (APD)
any	2	Y

BE: A Bus Error is sent back to the DAP setting its sticky bit error.

APD: Access port disabled. The transaction is discarded, the Debug Port (DP) sticky bit error is set.

Note: Refer to the ARM Debug Interface Architecture Specification for details.