OnCE™ Module

The user can poll the OSR in debug or user mode provided that the OnCE state machine is in the STATCOM state and the JTAG state machine is in Shift-DR. The OSR will capture new status only when traversing to the STATCOM state from a state other than STATCOM itself; see Section 12.3.3, “OnCE State Machine and Control Block.”

12.10.5.4 Setting Breakpoints in User Mode

Setting breakpoints in user mode is done the same way as in debug mode, except that it is recommended that the user disable breakpoints before writing to the OMAC, OBAR, or the BK4–BK0 bits in OCR. This avoids generating any indeterminate results that could arise if a breakpoint is occurring while the preceding registers are being modified.

12.10.5.5 Reading Pipeline Information in User Mode

The user can access pipeline information while the program is still executing. One way of doing this is for the user to follow these steps:

1.Make sure breakpoints and trace are disabled.

2.Write 01 to the EM bits in OCR.

3.Set the OCNTR to 1.

4.Set BK4-BK0 in the OCR to 10111 to enable trace mode.

5.Poll the OSR until TO equals 1.

6.Read the FIFO.

12.10.5.6 Displaying a Specified Register

The multiple DSP configuration shown in Figure 12-25 is used for Example 12-1. The user must assume before the procedure begins that all three DSPs are running and that their JTAG ports are executing the BYPASS instruction. The user wishes to display the value of a register (“reg”) of DSP#2.

Figure 12-25. Multiple DSP Configuration for Example Procedures

Accessing the OnCE Module

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.”

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

Example 12-1. Display a Specified Register—Serial

1.Enter Shift-IR, shift in BYPASS to DSP#1 and DSP#3, and DEBUG_REQUEST to DSP#2 (12 clocks in Shift-IR). Pass through Update-IR. OnCE state machine of DSP#2 is in STATCOM state.

2.Enter Shift-IR, ENABLE_ONCE into DSP#2 and BYPASS into others. Pass through Update-IR. OnCE state machine is in STATCOM state.

3.Enter Shift-DR. Begin polling to see if DSP#2 has entered debug mode (or poll via JTAG IR if STOP or WAIT may be executing). When status information indicates the core has

halted and is in debug mode, enter Shift-DR, shift in WRITE OPDBR with GO and no EX (OnCE command = 01001001). Pass through Update-DR. OnCE state machine is in WPDBR state.

4.Enter Shift-DR. Send the 16-bit opcode: MOVE reg, x:OGDB (17 clocks in Shift-DR). Pass through Update-DR to actually write the OPDBR and begin execution of the MOVE instruction. OnCE state machine is in STATCOM state to allow for polling.

5.Enter Shift-DR and begin polling for OS[1:0] = 11 again. While polling, shift in READ OPGDBR (OnCE command = 11001000). When OS[1:0] = 11, pass through Update-DR. In this case, polling really would not be necessary unless internal wait states are inserted. If they are, the user should reduce JTAG clock speed enough such that polling still is not necessary. OnCE state machine is in RWREG state in preparation for reading of OPGDBR.

6.Enter Shift-DR. Clock 17 times to display the value in the OGDBR (that is, register contents). Pass through Update-DR. OnCE state machine is in STATCOM state in preparation for further OnCE commands to be shifted in.