7.6. Privileged instructions

The coprocessor can restrict certain instructions for use in privileged modes only. To do this, the coprocessor tracks the nCPTRANS output. Figure 7.6 shows how nCPTRANS changes after a mode change.

Figure 7.6. Privileged instructions

The first two CHSDE[1:0] responses are ignored by the ARM9E-S because it is only the final CHSDE[1:0] response, as the instruction moves from Decode into Execute, that counts. This allows the coprocessor to change its response as nCPTRANS changes.

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