ARM ARM7TDMI User Manual Page 68
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Programmer’s Model
2-26 Copyright © 2001 ARM Limited. All rights reserved. ARM DDI 0234B
2.10 Interrupt latencies
Interrupt latencies are described in:
• Maximum interrupt latencies
• Minimum interrupt latencies.
2.10.1 Maximum interrupt latencies
When FIQs are enabled, the worst-case latency for FIQ comprises a combination of:
•T
syncmax
, the longest time the request can take to pass through the synchronizer.
T
syncmax
is two processor cycles.
•T
ldm
, the time for the longest instruction to complete. (The longest instruction is
an
LDM
that loads all the registers including the PC.) T
ldm
is 20 cycles in a zero wait
state system.
•T
exc
, the time for the Data Abort entry. T
exc
is three cycles.
•T
fiq
, the time for FIQ entry. T
fiq
is two cycles.
The total latency is therefore 27 processor cycles, slightly less than 0.7 microseconds in
a system that uses a continuous 40MHz processor clock. At the end of this time, the
ARM7TDMI-S executes the instruction at
0x1c
.
The maximum IRQ latency calculation is similar, but must allow for the fact that FIQ,
having higher priority, might delay entry into the IRQ handling routine for an arbitrary
length of time.
2.10.2 Minimum interrupt latencies
The minimum latency for FIQ or IRQ is the shortest time the request can take through
the synchronizer, T
syncmin
plus T
fiq
(four processor cycles).
- 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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