
RM0453 Rev 2
RM0453
Debug support (DBG)
1441
A DWT comparator compares the value held in its DWT_COMPxR registers with one of the
following:
•
a data address
•
an instruction address
•
a data value
•
the cycle count value, for comparator 0 only.
For address matching, the comparator can use a mask, so it matches a range of addresses.
On a successful match, the comparator generates one of the following:
•
one or more DWT data trace packets, containing one or more of:
–
the address of the instruction that caused a data access
–
an address offset, bits[15:0] of the data access address
–
the matched data value
•
a watchpoint debug event, on either the PC value or the accessed data address
•
a CMPMATCH[N] event that signals the match outside the DWT unit
A watchpoint debug event either generates a DebugMonitor exception or causes the
processor to halt execution and enter Debug state.
For more details on how to use the DWT, refer to the Arm
®
v7-M Architecture Reference
Manual
38.6.1
DWT control register (DWT_CTRLR)
Address offset: 0x000
Reset value: 0x4000 0000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
NUMCOMP[3:0]
NOTR
CPKT
NOEXT
TRIG
NOCYC
CNT
NOPRF
CNT
Res.
CYCEV
TENA
FOLDE
VTENA
LSUEV
TENA
SLEEPEVT
ENA
EXCEVT
ENA
CPIEV
TENA
EXCTRC
ENA
r
r
r
r
r
r
r
r
rw
rw
rw
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Res. Res. Res.
PCSAMPL
ENA
SYNCTAP[1:0]
CYCTAP
POSTINIT[3:0]
POSTPRESET[3:0]
CYCCNT
ENA
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
Bits 31:28
NUMCOMP[3:0]:
number of comparators implemented (read only)
0x4: Four comparators
Bit 27
NOTRCPKT:
trace sampling and exception tracing support (read only)
0: Supported
Bit 26
NOEXTTRIG:
external match signal, CMPMATCH support (read only)
0: Supported
Bit 25
NOCYCCNT:
cycle counter support (read only)
0: Supported
Bit 24
NOPRFCNT:
profiling counter support (read only)
0: Supported
Bit 23 Reserved, must be kept at reset value.