8.9.3. Determining system control coprocessor state

In order to access the System Control Coprocessor registers, debug state must be entered by a breakpoint, watchpoint or debug request. This ensures that the ARM7DMT core stops execution of code which may be dependent on the System Control Coprocessor.

Scan Chain 15 can then be selected via the SCAN_N instruction.

Instructions may then be scanned down the scan chain as if being executed from the ARM7DMT core. As the ARM7DMT is idle while Scan Chain 15 is being accessed, it is necessary to provide the register data via the scan chain. The instruction prior to the data must have the instruction/data flag cleared.

The data operation requires an additional clock from the TAP controller. This may be achieved by remaining in the RUN-TEST-IDLE state for an additional TCK cycle.

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