Mips Technologies R4000 - Hardware Interrupts; Nonmaskable Interrupt (NMI)

Chapter 12
372 MIPS R4000 Microprocessor User's Manual
Intervention and Snoop Requests
Figure 12-48 shows the format of an intervention request; Figure 12-49
shows the format of a snoop request. Table 12-23 lists the encodings of
SysCmd(4:0) for intervention requests; Table 12-24 lists the encodings
SysCmd(4:0) for snoop requests.
Figure 12-48 Intervention Request SysCmd Bus Bit Definition
Table 12-23 Encodings of SysCmd(4:0) for Intervention Requests
SysCmd(4)
Processor Unacknowledged Invalidate or Update
Cancellation
0 Update or Invalidate cancelled
1 No cancellation
SysCmd(3) Response to Dirty or Exclusive State
0
Return cache line data if in the dirty exclusive or dirty
shared state
1
Return cache line data if in the clean exclusive or dirty
exclusive state
SysCmd(2:0) Cache State Change Function
0 No change to cache state
1
If cache state is clean exclusive, change to shared;
otherwise no change to cache state
2
If cache state is clean exclusive or shared, change to
invalid; otherwise no change to cache state
3
If cache state is clean exclusive, change to shared; if cache
state is dirty exclusive, change to dirty shared; otherwise
make no change to cache state
4
If cache state is clean exclusive, dirty exclusive, or dirty
shared, change to shared; otherwise make no change to
cache state
5 Change to invalid regardless of current cache state
6 Reserved
7 Reserved
110
0
8 7 5 4 03 2
Intervention Request Specific
(see table)