
RCPU
REFERENCE MANUAL
DEVELOPMENT SUPPORT
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MOTOROLA
8-3
Assertion or negation of VSYNC.
Exception taken.
Indirect branch taken.
Execution of the following sequential instructions:
rfi
,
isync
,
mtmsr
, and
mtspr
to CMPA–CMPF, ICTRL, ECR, and DER.
When a program trace recording is needed, the user can ensure that cycles that
result from an indirect change-of-flow are visible on the external bus. The user can
do this in one of two ways: by setting the VSYNC bit, or by programming the ISCTL
bits in the I-bus support control register. Refer to
8.1.2 Instruction Fetch Show
Cycle Control
for more information.
When the processor is programmed to generate show cycles on the external bus
resulting from indirect change-of-flow, these cycles can generate regular bus cy-
cles (address phase and data phase) when the instructions reside in one of the ex-
ternal devices, or they can generate address-only show cycles for instructions that
reside in an internal device such as I-cache or internal ROM.
8.1.1.1 Marking the Indirect Change-of-Flow Attribute
When an instruction fetch cycle that results from an indirect change-of-flow is an
internal access (e.g., access to an internal memory location, or a cache hit during
an access to an external memory address), the indirect change-of-flow attribute is
indicated by the assertion (low) of the WR pin during the external bus show cycle.
When an instruction fetch cycle that results from an indirect change-of-flow is an
access to external memory not resulting in a cache hit, the indirect change-of-flow
attribute is indicated by the value 0001 on the CT[0:3] pins.
Table 8-1
summarizes the encodings that represent the indirect change-of-flow at-
tribute. In all cases the AT1 pin is asserted (high), indicating the cycle is an instruc-
tion fetch cycle.
Refer to
8.1.3 Program Flow-Tracking Pins
for more information on the use of
these pins for program flow tracking.
8.1.1.2 Sequential Instructions with the Indirect Change-of-Flow Attribute
Because certain sequential instructions (
rfi
,
isync
,
mtmsr
, and
mtspr
to CMPA –
CMPF, ICTRL, ECR, and DER) affect the machine in a manner similar to indirect
Table 8-1 Program Trace Cycle Attribute Encodings
CT[0:3]
AT1
WR
Type of Bus Cycle
0001
1
1
External bus cycle
01xx,
10xx,
110x
1
0
Show cycle on the external bus reflecting
an access to internal register or memory
or a cache hit
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.