MPC555
/
MPC556
DEVELOPMENT SUPPORT
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
21-3
The status pins are divided into two groups and one special case listed below:
21.2.1.1 Instruction Queue Status Pins — VF [0:2]
Instruction queue status pins denote the type of the last fetched instruction or how
many instructions were flushed from the instruction queue. These status pins are used
for both functions because queue flushes only happen in clocks that there is no fetch
type information to be reported.
Possible instruction types are defined in
.
shows VF[0:2] encodings for instruction queue flush information.
Table 21-1 VF Pins Instruction Encodings
VF[0:2]
Instruction Type
VF Next Clock Will Hold
000
None
More instruction type information
001
Sequential
More instruction type information
010
Branch (direct or indirect)
not
taken
More instruction type information
011
VSYNC was asserted/negated and therefore the
next instruction will be marked with the indirect
change-of-flow attribute
More instruction type information
100
Exception taken — the target will be marked with the
indirect change-of-flow attribute
Queue flush information
1
NOTES:
1. Unless next clock VF=111. See below.
101
Branch indirect taken,
rfi
,
mtmsr
,
isync
and in some
cases
mtspr
to CMPA-F, ICTRL, ECR, or DER —
the target will be marked with the indirect change-of-
flow attribute
2
2. The sequential instructions listed here affect the machine in a manner similar to indirect branch instructions.
Refer to
21.2.3 Sequential Instructions Marked as Indirect Branch
Queue flush information
110
Branch direct taken
Queue flush information
111
Branch (direct or indirect)
not
taken
Queue flush information
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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