Saving Pipeline Information; Reading The Trace Buffer - Motorola DSP56305 User Manual

The external command controller can analyze the information shifted out and detect
whether the chip has entered the Debug mode.
Note: JTAG compliance requires a preamble of 01 prior to shifting out status
information.

10.12.3 Saving Pipeline Information

The debugging activity is accomplished by means of DSP56300 core instructions
supplied from the external command controller. Therefore, the current state of the
DSP56300 core pipeline must be saved prior to starting the debug activity and of course
the state must be restored prior to returning to the Normal mode of operation. Following
is the description of the saving procedure (assume that ENABLE_ONCE has been
executed and Debug mode has been entered and verified, as described in Checking
Whether the Chip has Entered the Debug Mode on page 10-24):
1. Select shift-DR. Shift in the "Read PDB". Pass through update-DR.
2. Select shift-DR. Shift out the 24-bit OPDB register. Pass through update-DR.
3. Select shift-DR. Shift in the "Read PIL". Pass through update-DR.
4. Select shift-DR. Shift out the 24-bit OPILR register. Pass through update-DR.
Note that there is no need to verify acknowledge between steps 1 and 2, as well as 3 and
4, because completion is guaranteed by design.

10.12.4 Reading the Trace Buffer

An optional step during debugging activity is reading the information associated with
the Trace buffer in order to enable an external program to reconstruct the full trace of the
executed program. Following is the description of the read Trace buffer procedure
(assume that all actions described in Saving Pipeline Information have been executed):
1. Select shift-DR. Shift in the "Read PABFR". Pass through update-DR.
2. Select shift-DR. Shift out the 16-bit OPABFR register. Pass through update-DR.
3. Select shift-DR. Shift in the "Read PABDR". Pass through update-DR.
4. Select shift-DR. Shift out the 16-bit OPABDR register. Pass through update-DR.
5. Select shift-DR. Shift in the "Read PABEX". Pass through update-DR.
MOTOROLA DSP56305 User's Manual
On-Chip Emulation Module
Examples of Using the OnCE
10-25