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Debug

ID012310 Non-Confidential, Unrestricted Access

2. Clear the WCR[0] Enable Watchpoint and the BCRb[0] Enable breakpoint bits in the read

words and write them back to the WCR and BCRb. Now the watchpoint and the

breakpoint are disabled.

3. Write the DMVA to the WVR register.

4. Write the context ID to the BVRb register.

5. Write to the WCR with its fields set as follows:

• WCR[20] enable linking bit set, to link this WRP with the BRP indicated by

WCR[19:16], BRPb in this example

• Binary representation of b into WCR[19:6] linked BRP field

• WCR byte address select, load/store access, Secure access field, and supervisor

access fields as required

• WCR[0] enable watchpoint bit set.

6. Write to the BCRb with its fields set as follows:

• BCRb[22:21] meaning of BVR bit set to b01, to indicate that the value loaded into

BVRb is to be compared against the CP15 Context ID Register.

• BCRb[20] enable linking bit, set

• BCR [15:14] Secure access set to b00

• BCRb[8:5] byte address select set to b1111

• BCRb[2:1] supervisor access set to b11

• BCRb[0] enable breakpoint bit set.

13.14.3 Setting software breakpoint debug events (BKPT)

To set a software breakpoint on a particular virtual address, the debug monitor target must

perform the following steps:

1. Read memory location and save actual instruction.

2. Write BKPT instruction to the memory location.

3. Read memory location again to check that the BKPT instruction has been written.

4. If it has not been written, determine the reason.

Note

Cache coherency issues might arise when writing a BKPT instruction. See Debugging in a

cached system on page 13-43.

13.14.4 Using the debug communications channel

To read a word sent by a DBGTAP debugger:

1. Read the DSCR register.

2. If DSCR[30] rDTRfull flag is clear, then go to 1.

3. Read the word from the rDTR, CP14 Debug Register c5.

To write a word for a DBGTAP debugger:

1. Read the DSCR register.

ARM ARM1176JZF-S User Manual

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