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14.9
Programming debug events
14.9.1
Reading registers using scan chain 7
14.9.2
Writing registers using scan chain 7
14.9.3
Setting breakpoints, watchpoints and vector traps
ARM DDI 0301H
ID012310
This section describes the following operations:
•
Reading registers using scan chain 7
•
Writing registers using scan chain 7
•
Setting breakpoints, watchpoints and vector traps
•
Setting software breakpoints on page 14-41.
A typical sequence for reading registers using scan chain 7 is as follows:
SCAN_N 7
EXTEST
REQ 1stAddr2Rd0 0
FOR(i=2; i <= Words2Read; i++) DO
LOOP
REQ ithAddr2Rd 0 0 Ready readData
UNTIL Ready==1
Save value in readData
ENDFOR
LOOP
REQ 0 0 0 Ready readData
UNTIL Ready==1
Save value in readData
A typical sequence for writing to a register using scan chain 7 is as follows:
SCAN_N 7
EXTEST
REQ 1stAddr2Wr 1stData2Wr 0b1
FOR(i=2; i <= Words2Write; i++) DO
LOOP
REQ ithAddr2Wr ithData2Wr 1 Ready
UNTIL Ready==1
ENDFOR
LOOP
REQ 0 0 0 Ready
UNTIL Ready==1
You can program a vector catch debug event by writing to CP14 debug vector catch register.
You can program a breakpoint debug event by writing to CP14 debug 64-69 breakpoint value
registers and CP14 debug 80-84 breakpoint control registers.
You can program a watchpoint debug event by writing to CP14 debug 96-97 watchpoint value
registers and CP14 debug 112-113 watchpoint control registers.
Note
An External Debugger can access the CP14 debug registers whether the processor is in Debug
state or not, so these debug events can be programmed on-the-fly, while the processor is in
ARM/Thumb/Jazelle state.
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; select ITR
;read request for register 1stAddr2read
; ith read request while waiting
; wait until the previous request completes
; null request while waiting
; wait until last request completes
; select ITR
; write request for register 1stAddr2write
; ith write request while waiting
; wait until the previous request completes
; null request while waiting
; wait until last request completes
Debug Test Access Port
14-40
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