7.6. Privileged instructions

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

Figure 7.6. ARM922T privileged instructions

In Figure 7.6 the mode change (marked with an asterisk) occurs as follows:


The first two CHSDE[1:0] responses are ignored by the ARM922T because it is only the final CHSDE[1:0] response, as the instruction moves from Decode into Execute, that is relevant. This allows the coprocessor to change its response as nCPTRANS changes.

Copyright © 2000, 2001 ARM Limited. All rights reserved.ARM DDI 0184B