Chapter 5. Debug Support
5-41
Background Debug Mode (BDM)
5.5.3.3.9 Synchronize PC to the PSTDDATA Lines (SYNC_PC)
The SYNC_PC command captures the current PC and displays it on the PSTDDATA outputs.
After the debug module receives the command, it sends a signal to the ColdFire processor
that the current PC must be displayed. The processor then forces an instruction fetch at the
next PC with the address being captured in the DDATA logic under control of CSR[BTB].
The specic sequence of PSTDDATA values is as follows:
1. Debug signals a SYNC_PC command is pending.
2. CPU completes the current instruction.
3. CPU forces an instruction fetch to the next PC, generates a PST = 0x5 value
indicating a taken branch and signals the capture of DDATA.
4. The instruction address corresponding to the PC is captured.
5. The PST marker (0x9–0xB) is generated and displayed as dened by CSR[BTB]
followed by the captured PC address.
The SYNC_PC command can be used to dynamically access the PC for performance
monitoring. The execution of this command is considerably less obtrusive to the real-time
operation of an application than a HALT-CPU/READ-PC/RESUME command sequence.
Command Formats:
Command Sequence:
Figure 5-37. SYNC_PC Command Sequence
Operand Data:
None
Result Data:
Command complete status (0xFFFF) is returned when the register
write is complete.
15
12
11
8
7
4
3
0
0x0
0x1
Figure 5-36. SYNC_PC Command Format
NOP
???
NEXT CMD
"CMD COMPLETE"
SYNC_PC