ARM ARM7TDMI User Manual Page 126
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Debugging Your System
5-22 Copyright © 2001 ARM Limited. All rights reserved. ARM DDI 0234B
MRC CP14, 0, Rd, C1, C0
Returns the value from the DCC data read register into the
destination register Rd.
Note
The Thumb instruction set does not contain coprocessor instructions, so it is
recommended that these are accessed using SWI instructions when in Thumb state.
5.10.2 Communications through the DCC
Messages can be sent and received through the DCC.
Sending a message to the debugger
When the processor wishes to send a message to the debugger, it must check that the
DCC data write register is free for use by finding out whether the W bit of the DCC
control register is clear.
The processor reads the DCC control register to check the status of the W bit:
• If W bit is clear, the DCC data write register is clear.
• If the W bit is set, previously written data has not been read by the debugger. The
processor must continue to poll the control register until the W bit is clear.
When the W bit is clear, a message is written by a register transfer to coprocessor 14.
As the data transfer occurs from the processor to the DCC data write register, the W bit
is set in the DCC control register.
The debugger sees both the R and W bits when it polls the DCC control register through
the JTAG interface. When the debugger sees that the W bit is set, it can read the comms
data write register and scan the data out. The action of reading this data register clears
the debug comms control register W bit. At this point the communications process can
begin again.
Receiving a message from the debugger
Transferring a message from the debugger to the processor is similar to sending a
message to the debugger. In this case, the debugger polls the R bit of the debug comms
control register:
• If the R bit is LOW, the comms data read register is free, and data can be placed
there for the processor to read.
- ARM7TDMI-S 1
- Contents 3
- Chapter 3 Memory Interface 4
- Chapter 6 ETM Interface 5
- Chapter 8 AC Parameters 5
- List of Tables 7
- List of Figures 10
- • Feedback on page xvi 11
- About this document 12
- Preface 13
- Other publications 15
- Architecture 15
- Feedback 16
- Chapter 1 17
- Introduction 17
- 1.2 ARM7TDMI-S architecture 20
- Figure 1-3 ARM7TDMI-S core 23
- 1.4.1 ARM instruction summary 26
- [Rn, #+/-12bit_Offset] 29
- [Rn, +/-Rm] 29
- [Rn, #+/-12bit_Offset]! 29
- [Rn, +/-Rm]! 29
- , is shown in Table 1-4 30
- [Rn, #+/-8bit_Offset] 31
- Register 31
- [Rn, #+/-(8bit_Offset*4)] 32
- Post-indexed 32
- Fields 33
- , are shown in Table 1-10 33
- Condition fields 33
- , are shown in Table 1-11 33
- Halfword 36
- POP <reglist> 38
- POP <reglist, PC> 38
- SWI 8bit_Imm 38
- 0x7F1F0F0F 40
- Chapter 2 43
- Programmer’s Model 43
- 2.3 Memory formats 46
- 2.4 Instruction length 48
- 2.5 Data types 49
- 2.6 Operating modes 50
- 2.7 Registers 51
- Table 2-2 PSR mode bit values 59
- MOV PC, R14 61
- MOVS PC, R14_svc 61
- MOVS PC, R14_und 61
- SUBS PC, R14_abt, #4 61
- SUBS PC, R14_fiq, #4 62
- SUBS PC, R14_irq, #4 62
- SUBS PC, R14_abt, #8 62
- UNPREDICTABLE 62
- SUBS PC,R14_fiq,#4 63
- SUBS PC,R14_abt,#8 65
- MOVS PC,R14_und 65
- 2.10 Interrupt latencies 68
- 2.11 Reset 69
- Chapter 3 71
- Memory Interface 71
- 3.2 Bus interface signals 73
- 3.3 Bus cycle types 74
- Table 3-2 Burst types 77
- Figure 3-5 Merged I-S cycle 79
- 3.4 Addressing signals 80
- 3.4.6 CPTBIT 82
- 3.5 Data timed signals 83
- Figure 3-6 Data replication 86
- Figure 3-7 Use of CLKEN 87
- Chapter 4 89
- 4.1 About coprocessors 90
- Table 4-2 Handshaking signals 94
- Signal Direction Meaning 94
- 4.5 Connecting coprocessors 99
- Coprocessor Interface 100
- 4.7 Undefined instructions 103
- 4.8 Privileged instructions 104
- Chapter 5 105
- Debugging Your System 105
- 5.2 Controlling debugging 109
- 5.3 Entry into debug state 111
- Figure 5-3 Debug state entry 112
- ARM7TDMI-Smacrocell 115
- 5.4 Debug interface 116
- EmbeddedICE-RT 118
- 5.7 Disabling EmbeddedICE-RT 120
- 5.9 Monitor mode debugging 122
- 0 RW...100 124
- MRC CP14, 0, Rd, C0, C0 125
- MCR CP14, 0, Rn, C1, C0 125
- MRC CP14, 0, Rd, C1, C0 126
- 5.12 The TAP controller 130
- 5.13 Public JTAG instructions 132
- 011112272831 135
- Part number 135
- Manufacturer identity 1 135
- 0x7f1f0f0f 136
- 5.15 Scan timing 140
- 31 DATA[30] Input/output 142
- 32 DATA[31] Input/output 142
- 33 DBGBREAK Input 142
- Number Signal Type 142
- 5.17 Exit from debug state 146
- 0 E0802000; ADD R2, R0, R0 148
- 1 E1826001; ORR R6, R2, R1 148
- MOV R0, R0 148
- SUB PC, PC, #28 148
- - (4 + N + 3S) 150
- - (3 + N + 3S) 150
- 8 67 5 34 2 01 154
- 5.21 Programming breakpoints 157
- 0xffffffff 158
- 0xdfffdfff 158
- 0x00000000 158
- 5.22 Programming watchpoints 159
- 5.23 Abort status register 160
- 5.24 Debug control register 161
- 5.25 Debug status register 164
- 5.27 EmbeddedICE-RT timing 169
- Chapter 6 171
- ETM Interface 171
- 6.1 About the ETM interface 172
- 6.4 Clocks and resets 176
- 6.5 Debug request wiring 177
- Chapter 7 179
- Instruction Cycle Timings 179
- MOV PC,R14 185
- STM..{R14} LDM..{PC} 185
- 7.4 Thumb branch with link 186
- 7.5 Branch and exchange 187
- 7.6 Data operations 188
- 7.8 Load register 192
- 7.9 Store register 194
- 7.10 Load multiple registers 195
- 7.11 Store multiple registers 197
- 7.12 Data swap 198
- 7.20 Unexecuted instructions 208
- Chapter 8 209
- AC Parameters 209
- 8.1 Timing diagrams 210
- Figure 8-2 Coprocessor timing 212
- 8.1.4 Debug timing 213
- 8.1.5 Scan timing 214
- Figure 8-5 Scan timing 215
- Appendix A 219
- Signal Descriptions 219
- A.1 Signal descriptions 220
- Appendix B 227
- ARM7TDMI 227
- B.1 Interface signals 228
- B.2 ATPG scan interface 232
- B.3 Timing parameters 233
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