Nec Network Controller uPD98502 Manual do Utilizador Página 138

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CHAPTER 2 V
R
4120A
138
Preliminary User’s Manual S15543EJ1V0UM
2.5.3.7 Exception program counter (EPC) register (14)
The Exception Program Counter (EPC) is a read/write register that contains the address at which processing
resumes after an exception has been serviced. Because the
µ
PD98502 does not support the MIPS16 instruction
mode, the EPC register contains either:
Virtual address of the instruction that caused the exception.
Virtual address of the immediately preceding branch or jump instruction (when the instruction associated with
the exception is in a branch delay slot, and the BD bit in the Cause register is set to 1).
The EXL bit in the Status register is set to 1 to keep the processor from overwriting the address of the exception-
causing instruction contained in the EPC register in the event of another exception.
Figure 2-54 shows the EPC register format.
Figure 2-54. EPC Register Format
(a) 32-bit mode
32
031
EPC
(b) 64-bit mode
64
063
EPC
EPC: Restart address after exception processing.
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