Freescale Semiconductor MCF5480 - Manual (Page 293)

Background Debug Mode (BDM)
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 8-43
Result Data: The command-complete response (0xFFFF) is returned during the next shift
operation.
8.5.3.3.8 No Operation ( NOP )
NOP performs no operation and may be used as a null command where required.
Command Formats:
Command Sequence:
Figure 8-38. NOP Command Sequence
Operand Data: None
Result Data: The command-complete response, 0xFFFF (with S cleared), is returned during the
next shift operation.
8.5.3.3.9 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 specific 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 defined by CSR[BTB] followed by the
captured PC address.
If the option to display ASID is enabled (CSR[3] = 1), the 8-bit ASID follows the address. That is, the
PSTDDATA sequence is {0x5, Marker, Instruction Address, 0x8, ASID}, where the 0x8 is the marker for
the ASID.
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:
15 12 11 8 7 4 3 0
0x0 0x0 0x0 0x0
Figure 8-37. NOP Command Format
NOP
???
NEXT CMD
’CMD COMPLETE’