User guide

Data Watchpoint and Trace Unit
ARM DDI 0337I Copyright © 2005-2008, 2010 ARM Limited. All rights reserved. 8-5
ID072410 Non-Confidential
DWT registers are described in the ARMv7M Architecture Reference Manual. Peripheral
Identification. Component Identification registers are described in the ARM CoreSight
Components Technical Reference Manual.
Note
• Cycle matching functionality is only available in comparator 0.
• Data matching functionality is only available in comparator 1.
• Data value is only sampled for accesses that do not produce an MPU or bus fault. The PC
is sampled irrespective of any faults. The PC is only sampled for the first address of a
burst.
• The FUNCTION field in the DWT_FUNCTION1 register is overridden for comparators
given by DATAVADDR0 and DATAVADDR1 if DATAVMATCH is also set in
DWT_FUNCTION1. The comparators given by DATAVADDR0 and DATAVADDR1 can
then only perform address comparator matches for comparator 1 data matches.
• If the data matching functionality is not included during implementation it is not possible
to set DATAVADDR0, DATAVADDR1, or DATAVMATCH in DWT_FUNCTION1. This
means that the data matching functionality is not available in the implementation. Test the
availability of data matching by writing and reading the DATAVMATCH bit in
DWT_FUNCTION1. If this bit cannot be set then data matching is unavailable.
• PC match is not recommended for watchpoints because it stops after the instruction. It
mainly guards and triggers the ETM.
0xE0001FF0 CID0 RO 0x0D Component identification registers
0xE0001FF4 CID1 RO 0xE0
0xE0001FF8
CID2 RO 0x05
0xE0001FFC
CID3 RO 0xB1
a. Possible reset values are:
0x40000000 if four comparators for watchpoints and triggers are present
0x4F000000 if four comparators for watchpoints only are present
0x10000000 if only one comparator is present
0x1F000000 if one comparator for watchpoints and not triggers is present
0x00000000 if DWT is not present.
Table 8-1 DWT register summary (continued)
Address Name Type Reset Description