Accessing the OnCE Module

Example 12-2. Display X Memory Area from Address xxxx—Serial (Continued)

9.Enter Shift-DR. Clock 17 times to display the value in the OGDBR (that is, the contents of memory location xxxx). Pass through Update-DR. OnCE state machine is in STATCOM state.

10.Enter Shift-DR. Shift in NO SELECTION with GO and no EX (OnCE command = 11000000). Pass through Update-DR to execute MOVE X:(R0)+, x:OGDB again. Go to step eight to continue reading memory contents. When finished, restore original value of R0.

12.10.5.8 Returning from Debug Mode to Normal Mode

For Example 12-3, the user should assume the multiple DSP configuration shown in Figure 12-25 on page 12-50. The user wishes to bring DSP#2 back into user mode from debug mode. DSP#1 and DSP#3 are in user mode and their JTAG ports are executing the BYPASS instruction.

NOTE:

“Shift-IR,” “Shift-DR,” “Update-IR,” and “Update-DR” in the following example refer to operating states in the JTAG module. The TAP controller in the JTAG module uses the current operating state of the TAP controller combined with the level of the TMS input to transition between the operating states. A detailed description of the TAP controller state machine is presented in Section 13.3, “TAP Controller.”

NOTE:

BYPASS, DEBUG_REQUEST, and ENABLE_ONCE are JTAG instructions. (See Table 13-2 on page 13-5 for a list of JTAG instructions.)

Example 12-3. Return from Debug Mode to Normal Mode—Serial

1.Enter Shift-DR, shift WRITE OPDBR with no GO and no EX (OnCE command = 00001001) into DSP#2 (9 clocks in Shift-DR). Pass through Update-DR. PAB is driven with value in OPABDR, which is the value latched from the PAB just before entering debug mode. OnCE state machine is in WPDBR state.

2.Enter Shift-DR. Send the saved contents of the OPDBR (17 clocks in Shift-DR). Pass through Update-DR to actually load the OPDBR. OPDBR will drive the PDB, and the instruction latch loads the value on the PDB. OnCE state machine is in the STATCOM state.

3.Enter Shift-DR, shift WRITE OPDBR with GO and EX (OnCE command = 01101001) into DSP#2 (9 clocks in Shift-DR). Pass through Update-DR. OnCE state machine is in WPDBR state.

4.Enter Shift-DR. Send the saved contents of the OPDBR (17 clocks in Shift-DR). Pass through Update-DR to actually load the OPDBR. The OnCE state machine goes into the IDLE state then back to STATCOM as long as ENABLE_ONCE is executing in JTAG machine. DSP#2’s core pipeline is restored to its state prior to debug, and the DSP is back in user mode.