ARM r1p3 40shows the values in the link register after exceptions, Following sections describe

Debug

Table 11-40shows the values in the link register after exceptions.

			Table 11-40 Values in link register after exceptions
Cause of fault	ARM	Thumb	Return address (RAa) meaning
Breakpoint	RA+4	RA+4	Breakpointed instruction address
Watchpoint	RA+8	RA+8	Watchpointed instruction address
BKPT instruction	RA+4	RA+4	BKPT instruction address
Vector catch	RA+4	RA+4	Vector address
Prefetch Abort	RA+4	RA+4	Address of the instruction where the execution can resume
Data Abort	RA+8	RA+8	Address of the instruction where the execution can resume

a.This is the address of the instruction that the processor can execute first on debug exception return. The address of the access that hit the watchpoint is in the WFAR.

The following sections describe:

•Effect of debug exceptions on CP15 registers and WFAR

•Avoiding unrecoverable states on page 11-43.

11.7.1Effect of debug exceptions on CP15 registers and WFAR

The four CP15 registers that record abort information are:

1.Data Fault Address Register (DFAR)

2.Instruction Fault Address Register (IFAR)

3.Instruction Fault Status Register (IFSR)

4.Data Fault Status Register (DFSR).

For more information on these registers, see Chapter 4 System Control Coprocessor.

If the processor takes a debug exception because of a watchpoint debug event, the processor performs the following actions on these registers:

•it does not change the IFSR or IFAR

•it updates the DFSR with the debug event encoding

•it writes an Unpredictable value to the DFAR

•it updates the WFAR with the address of the instruction that accessed the watchpointed address, plus a processor state dependent offset:

—+ 8 for ARM state

—+ 4 for Thumb state.

If the processor takes a debug exception because of a breakpoint, BKPT, or vector catch debug event, the processor performs the following actions on these registers:

•it updates the IFSR with the debug event encoding

•it writes an Unpredictable value to the IFAR

•it does not change the DFSR, DFAR, or WFAR.

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