18.4.5.2.3 CPU Reset Extension

On cold-plugging attachment, the DSU sets the STATUSA.CRSTEXT0 bit, which forces the CPU into a Reset state until the bit is cleared. This ensures that the CPU is not executing code and is in a known state when a debugger connects.

To release the CPU from reset, the debugger writes a '1' to clear STATUSA.CRSTEXT0. On Reset extension release, CPU0 starts executing instructions.