Motorola 24-Bit Digital Signal Processor, DSP56000 - page 218

USING THE OnCE
10- 26 ON-CHIP EMULATION (OnCE) MOTOROLA
10.11.4 Executing a Single-Word DSP56K Instruction While in Debug Mode
1. Send command WRITE PDB REGISTER, GO, no EX (01001001).
The OnCE controller selects PDB as destination for serial data.
2. ACK
3. Send the single-word 24-bit DSP56K opcode to be executed.
After 24 bits have been received, the PDB register drives the PDB. The OnCE con-
troller releases the chip from the debug mode and the chip executes the instruction.
The signal that marks the end of the instruction returns the chip to the debug mode.
Some DSP56K instructions should not be executed in this state: DO, REP, ILLE-
GAL or any opcode that is considered illegal, and DEBUG.
4. ACK
10.11.5 Executing a Two-Word DSP56K Instruction While in Debug Mode
1. Send command WRITE PDB REGISTER, no GO, no EX (00001001).
The OnCE controller selects PDB as destination for serial data.
2. ACK
3. Send the first instruction word (24-bit DSP56K opcode)
After 24 bits have been received, the PDB register drives the PDB. The OnCE con-
troller causes the processor to load the opcode.
Some DSP56K instructions should not be executed in this state: DO, REP, ILLE-
GAL or any opcode that is considered illegal, and DEBUG.
4. ACK
5. Send command WRITE PDB REGISTER, GO, no EX (01001001)
The OnCE controller selects PDB as destination for serial data.
6. ACK
7. Send the second 24-bit instruction word.
After 24 bits have been received, the PDB register drives the PDB. The OnCE con-
troller releases the chip from the debug mode and the instruction starts execution.
The signal that marks the end of the instruction returns the chip to the debug mode.
8. ACK
10.11.6 Returning from Debug Mode to Normal Mode
There are two cases for returning from the debug mode in a single processor:
• Control is returned to the program that was running before debug was initiated.
• Jump to a different program location is executed.