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PROGRAMMER'S MODEL ARM920T PROCESSOR
2-24
Changing the ProcID - performing a fast context switch
A fast context switch is done by writing to CP15 register 13. The contents of the caches and TLBs do not have to be
flushed after a fast context switch because they still hold valid address tags. It should be noted that the two
instructions after the MCR to write the ProcID will have been fetched with the old ProcID:
{ProcID = 0}
MOV r0, #1:SHL:25 ; Fetched with ProcID = 0
MCR p15,0,r0,c13,c0,0 ; Fetched with ProcID = 0
A1 ; Fetched with ProcID = 0
A2 ; Fetched with ProcID = 0
A3 ; Fetched with ProcID = 1
REGISTER 15: TEST CONFIGURATION REGISTER
Register 15 is used for test purposes. Accessing (reading or writing) this register will cause the ARM920T to have
unpredictable behavior.