System Development and Debugging
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
53-3
A cycle marked with the program trace cycle attribute is generated when entering and exiting VSYNC
state by setting TECR[VSYNC].
53.1.3
Program Trace Signals
Note that if the MPC885 is in half-speed bus mode (SCCR[EBDF] = 0b01), the VF and VFLS pins
do not report fetch and flush information for the program trace capability. However, the internal
freeze state of the processor is reported in the VFLS pins as it does in full-speed bus mode. The
status pins are divided into two groups, shown in
Table 53-2
.
Table 53-3
describes possible instruction queue flushes as they are identified by VF encodings.
Table 53-1. Fetch Show Cycles Control
VSYNC
ICTRL[ISCT_SER] Instruction Fetch Show Cycle Control Bits
Show Cycles Generated
X
000
All fetch cycles
X
X01
All change of flow (direct and
indirect)
X
X10—Enable STS functionality of OP2/MODCK1/STS by writing 10
or 11 to SIUMCR[DBGC]. The external bus address should be
sampled only when STS is asserted.
All indirect change of flow
0
X11
No show cycles are performed
1
X11
All indirect change of flow
Table 53-2. Status Pin Groupings
Pins
Description
VF [0–2]
Instruction queue status. Denotes the type of the last fetched instruction or how many instructions were
flushed from the instruction queue. VF [0–2] are used for both functions because queue flushes occur
only in clocks in which no fetch type information is reported.
Table 53-3
defines instruction queue flushes
and
Table 53-4
defines instruction fetch types.
VFLS [0–1] History buffer flushes status: indicates the number of instructions that are flushed from the history buffer
on this clock. Possible values are as follows:
00 None
01 1 instruction was flushed from the history buffer
10 2 instructions were flushed from the history buffer
11 Used for debug mode indication. Should be ignored by the program trace external hardware. See
Section 53.3.1, “Debug Mode Operation.”
Table 53-3. VF Pins Encoding: Instruction Queue Flushes
VF
Instructions Flushed
VF Next Cycle Holds
000
None
Instruction type information
001
One instruction was flushed from the instruction queue
Instruction type information
010
Two instructions were flushed from the instruction queue
Instruction type information
011
Three instructions were flushed from the instruction queue
Instruction type information
Summary of Contents for PowerQUICC MPC870
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