OnCE™ Module

12.10.5.9 Recovering from STOP or WAIT Execution

If a STOP or WAIT instruction is executed while the user is accessing OnCE in user mode, problems will occur since few or no internal clocks are running anymore. This possibility should be avoided; the user can recognize the occurrence by capturing the OS bits in the JTAG IR in Capture-IR. The user can then choose to send a DEBUG_REQUEST to bring the core out of STOP or WAIT.

12.11 Using the OnCE Port

Following are example OnCE port command sequence for performing common debugging tasks. Entering and exiting debug mode, reading registers and memory, and restarting execution at a new address are discussed.

12.11.1 Beginning Debug Activity

Debug activity begins on an instruction boundary after the debug request pin is asserted, a DEBUGcc opcode is executed, a trigger event occurs, or a JTAG DEBUG_REQUEST is executed. If the instruction executing when the debug request pin is asserted is a REP instruction or the instruction following a REP instruction, then the debug activity begins after the instruction following the REP instruction finishes its repetitions. The first ACK indicates that the OnCE controller is ready to receive commands and data. Most of the debug activities will have the beginning specified in Example 12-4.

Example 12-4. Begin Debug Activity

Wait for acknowledge on DS line

1.Save pipeline information:

a)Send command Read OPDBR (OnCE command = 11001001)

b)Wait for acknowledge on DS line.

c)Issue 16 clocks to read out data from selected register.

d)Send command READ OPGDR (OnCE command = 11001000)

e)Wait for acknowledge on DS line.

f)Issue 16 clocks to read out data from selected register.

2.Read PAB FIFO and fetch/decode info (this step is optional):

a)Send command READ OPABFR (OnCE command = 11001010)

b)Wait for acknowledge on DS line.

c)Issue 16 clocks to read out data from selected register.

d)Send command READ OPABDR (OnCE command = 11010011)

e)Wait for acknowledge on DS line.

f)Issue 16 clocks to read out data from selected register.

Using the OnCE Port

Example 12-4. Begin Debug Activity (Continued)

g)Send command READ OPFIFO (OnCE command = 11010001)

h)Wait for acknowledge on DS line.

i)Issue 16 clocks to read out data from selected register.

j)Send command READ OPFIFO (OnCE command = 11010001)

k)Wait for acknowledge on DS line.

l)Issue 16 clocks to read out data from selected register.

m)Send command READ OPFIFO (OnCE command = 11010001)

n)Wait for acknowledge on DS line.

o)Issue 16 clocks to read out data from selected register.

p)Send command READ OPFIFO (OnCE command = 11010001)

q)Wait for acknowledge on DS line.

r)Issue 16 clocks to read out data from selected register.

s)Send command READ OPFIFO (OnCE command = 11010001)

t)Wait for acknowledge on DS line.

u)Issue 16 clocks to read out data from selected register.