Motorola MPC533 Reference Manual page 882

Watchpoints and Breakpoints Support
VF
000 0 Instructions flushed from instruction queue
001 1 Instructions flushed from instruction queue
010 2 Instructions flushed from instruction queue
011 3 Instructions flushed from instruction queue
100 4 Instructions flushed from instruction queue
101 5 Instructions flushed from instruction queue
110 Reserved
111 Branch (direct or indirect) NOT taken (misprediction)
Encoding VF equal to 0b111 for the queue flush information
indicates that the predicted branch (indicated in the previous
clock by appropriate VF encoding) is cancelled, and that
further flush information follows in the next clock.
The VFLS signals track the history buffer flushes. This aids the READI module to
determine how many instructions actually executed and retired. Refer to Table 21-8 for
details on VFLS encoding.
Table 21-8. VFLS History Buffer Flush Encoding
VFLS
The history buffer has a queue depth of six instructions, but can
flush (restore processor state) up to two instructions at a time.
Using the RCPU program trace information available via the VF and the VFLS signals, and
snooping the U-bus for instruction fetches, the READI module generates program trace
messages to track the change of flow for the RCPU.
21.2 Watchpoints and Breakpoints Support
Watchpoints, when detected, are reported to the external world on dedicated pins but do not
change the timing and the flow of the machine. Breakpoints, when detected, force the
21-12
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Table 21-7. VF Queue Flush Information
Instruction Type
History Buffer Flush Information
00 0 Instructions flushed from History Buffer
01 1 Instructions flushed from History Buffer
10 2 Instructions flushed from History Buffer
11 Ignored for Program Trace
MPC533 Reference Manual
NOTE
NOTE
Next VF Encoding
Instruction Type
Queue Flush Information
MOTOROLA