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ARM DDI 0301H
ID012310
Scan out 40 bits. If Ready/nRW is 0, then repeat this step. If Ready/nRW is 1, the first read
request has completed successfully and the next scanned-out 32 bits are the requested
value. The second read request was placed at the Update-DR state.
3.
Scan in the address 0, the rest of the fields are not important.
Scan out 40 bits. If Ready/nRW is 0, then repeat this step. If Ready/nRW is 1, the second
read request has completed successfully and the next scanned-out 32 bits are the requested
value. The scanned-in null request has avoided the generation of another request.
The register map is similar to the one of CP14 debug, and Table 14-2 lists it.
Address[6:0]
b0000000
b0000001-b0000110
b0000111
b0001000
b0010011-b0111111
b1000000-b1000101
b1000110-b1001111
b1010000-b1010101
b1010110-b1011111
b1100000-b1100001
b1100010-1b101111
b1110000-b1110001
b1110010-b1111111
a. y is the decimal representation for the binary number Address[3:0]
The following points apply to the use of scan chain 7:
•
Every time there is a request to read the PC, a sample of its value is copied into scan chain
7. Writes are ignored. The sampled value can be used for profiling of the code. See
Interpreting the PC samples on page 14-20 for details of how to interpret the sampled
value.
•
The external program counter sample register always reads
when the core is in a mode when Non-invasive debug is not permitted.
•
When accessing registers using scan chain 7, the processor can be either in Debug state or
in normal state. This implies that breakpoints, watchpoints, and vector traps can be
programmed through the Debug Test Access Port even if the processor is running.
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Table 14-2 Scan chain 7 register map
Register number
Abbreviation
0
NULL
1-6
-
7
VCR
8
PC
19-63
-
64-69
BVRy
70-79
-
80-85
BCRy
86-95
-
96-97
WVRy
98-111
-
112-113
WCRy
114-127
-
Debug Test Access Port
Register name
No request register
Reserved
Vector catch register
Program counter
Reserved
a
Breakpoint value registers
Reserved
a
Breakpoint control registers
Reserved
Watchpoint value registers
a
Reserved
a
Watchpoint control registers
Reserved
in Debug state or
0xFFFFFFFF
14-19
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