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Debug in Depth

B.13 Programming breakpoints

Breakpoints are classified as hardware breakpoints or software breakpoints:

Hardware breakpoints

Typically monitor the address value and can be set in any code, even in

code that is in ROM or code that is self-modifying.

Software breakpoints on page B-48

Monitor a particular bit pattern being fetched from any address. One

EmbeddedICE-RT watchpoint can therefore be used to support any

number of software breakpoints. Software breakpoints can normally be

set only in RAM because a special bit pattern chosen to cause a software

breakpoint has to replace the instruction.

B.13.1 Hardware breakpoints

To make a watchpoint unit cause hardware breakpoints on instruction fetches:

1. Program its address value register with the address of the instruction to be

breakpointed.

2. For an ARM-state breakpoint, program bits [1:0] of the address mask register to

b11. For a breakpoint in Thumb state, program bits [1:0] of the address mask

3. Program the data value register if you require a data-dependent breakpoint. (A

data-dependent breakpoint is one that matches the instruction code fetched as

well as the address.) Ensure that you clear all the bits in the data mask register.

If the data value is not required, program the data mask register to

0xFFFFFFFF

(all

bits set).

4. Program the control value register with nOPC = 0.

5. Program the control mask register with nOPC = 0.

6. When you have to make the distinction between User and non-User mode

instruction fetches, program the nTRANS value and mask bits appropriately.

7. If required, program the EXTERN, RANGE, and CHAIN bits in the same way.

8. Program the mask bits for all unused control values to 1.

Brand

Model

ARM7TDMI

ARM ARM7TDMI User Manual

Other manuals for ARM ARM7TDMI