Arm Cortex R4F Manuel d'utilisateur Page 52
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Programmer’s Model
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2.5 Memory formats
The processor views memory as a linear collection of bytes numbered in ascending order from
zero. For example, bytes 0-3 hold the first stored word, and bytes 4-7 hold the second stored
word.
The processor can treat words of data in memory as being stored in either:
• Byte-invariant big-endian format
• Little-endian format.
Additionally, the processor supports mixed-endian and unaligned data accesses. For more
information, see the ARM Architecture Reference Manual.
2.5.1 Byte-invariant big-endian format
In byte-invariant big-endian (BE-8) format, the processor stores the most significant byte of a
word at the lowest-numbered byte, and the least significant byte at the highest-numbered byte.
Figure 2-1 shows byte-invariant big-endian (BE-8) format.
Figure 2-1 Byte-invariant big-endian (BE-8) format
2.5.2 Little-endian format
In little-endian format, the lowest-numbered byte in a word is the least significant byte of the
word and the highest-numbered byte is the most significant. Figure 2-2 shows little-endian
format.
Figure 2-2 Little-endian format
Memory Register
Address
A[31:0]
+1
msbyte
lsbyte
+2
+3
B0
07
B1
B3B2B0 B1
31 24 23 16 15 8 7 0
B2
B3
Memory Register
Address
A[31:0]
+1
msbyte
lsbyte
+2
+3
b0
07
b1
b0b1b3 b2
31 24 23 16 15 8 7 0
b2
b3
- -R4 and Cortex-R4F 1
- Cortex-R4 and Cortex-R4F 2
- Contents 3
- Chapter 15 AC Characteristics 5
- Appendix B ECC Schemes 6
- Appendix C Revisions 6
- List of Tables 10
- List of Figures 13
- • Feedback on page xxi 16
- About this book 17
- Preface 18
- Feedback 21
- Chapter 1 22
- Introduction 22
- 1.1 About the processor 23
- 1.2 About the architecture 24
- AXI master bus 25
- AXI slave bus 25
- 1.5 Power management 33
- 1.6 Configurable options 34
- 0xFFFF0000 36
- 1.7 Execution pipeline stages 38
- 1.8 Redundant core comparison 40
- 1.9 Test features 41
- Chapter 2 47
- Programmer’s Model 47
- 2.2 Instruction set states 49
- 2.3 Operating modes 50
- 2.4 Data types 51
- 2.5 Memory formats 52
- 2.6 Registers 53
- Program status registers 55
- 2.7 Program status registers 56
- 2.8 Exceptions 62
- LDM ..,{..pc}^ 63
- SUBS PC, R14_irq, #4 64
- SUBS PC, R14_fiq, #4 65
- Register on page 4-35 67
- Imprecise abort masking 69
- Memory barriers 69
- Chapter 3 76
- 3.1 Initialization 77
- 3.2 Resets 81
- 3.3 Reset modes 82
- 3.4 Clocking 84
- Chapter 4 85
- VariantImplementor 98
- 31 23 20 19 16 15 4 3 0 98
- 29 28 19 18 16 15 3 2 0 100
- SReserved 101
- 31 16 8 7 1 0 101
- ReservedDRegion 101
- System Control Coprocessor 102
- Security extension 103
- ARMv4 Programmer’s model 103
- 31 12 11 8 7 4 3 0 103
- Reserved 103
- 0x00000000 105
- Reserved FCSE TCM PMSA VMSA 106
- Auxiliary Control Register 106
- Cache coherence 106
- Outer shareable 106
- Exclusive instructions 115
- Barrier instructions 115
- SMC instructions 115
- Reserved Level 119
- IRQ = 0x18 120
- 0x0000001C 121
- 0xFFFF0000-0xFFFF001C 121
- Bits Field Function 134
- [4:0] Reserved SBZ 134
- Reserved Region 137
- Figure 4-38 Cache operations 139
- Base address 142
- 31 12 11 7 6 2 1 0 142
- Reserved Size 142
- Privilege access 144
- AXI slave enable 144
- 31 16 15 78430 153
- [11:0] Reserved SBZ 156
- Chapter 5 160
- Prefetch Unit 160
- 5.1 About the prefetch unit 161
- 5.2 Branch prediction 162
- 5.3 Return stack 164
- Chapter 6 165
- 6.1 About the events 166
- 6.2 About the PMU 170
- 6.4 Event bus interface 183
- Chapter 7 184
- Memory Protection Unit 184
- 7.1 About the MPU 185
- Region 1 188
- Region 2 188
- Guard region 189
- 7.2 Memory types 190
- 7.3 Region attributes 192
- 7.5 MPU faults 195
- Chapter 8 197
- Level One Memory System 197
- 8.3 Fault handling 203
- 8.4 About the TCMs 209
- 8.5 About the caches 214
- Clean data cache by set/way 221
- 8.8 Error detection events 232
- Chapter 9 234
- Level Two Interface 234
- 9.1 About the L2 interface 235
- 9.2 AXI master interface 236
- LDMIA R10, {R0-R5} 250
- R10 = 0x1010 250
- 9.4 AXI slave interface 253
- 0x10000000 265
- Chapter 10 266
- Power Control 266
- 10.1 About power control 267
- 10.2 Power management 268
- Chapter 11 270
- 11.1 Debug systems 271
- 11.2 About the debug unit 272
- 11.3 Debug register interface 274
- DSAR CP14 c0, Debug Self 279
- Valid bits 281
- 31 12 11 2 1 0 281
- Bits Reset value Description 292
- Breakpoint value 292
- 0x00000007 293
- 0x0000000F 293
- 0x0000001F 293
- 0x7FFFFFFF 293
- 0xFFFFFFFC 294
- Lock implemented bit 298
- 11.5 Management registers 301
- Claim tag set 302
- 0xC5ACCE55 303
- Register number Function 305
- 11.6 Debug events 308
- 11.7 Debug exception 310
- — + 8 for ARM state 311
- 11.8 Debug state 313
- 11.9 Cache debug 319
- Example 11-15 Reading the PC 333
- Reading memory 334
- Chapter 12 342
- FPU Programmer’s Model 342
- Figure 12-1 FPU register bank 344
- 12.3 System registers 345
- Implementer Part number 346
- 31 24 23 22 16 15 8 7 4 3 0 346
- SVRM TE SPSR D DP 349
- Reserved I DNSP LS 350
- 12.4 Modes of operation 351
- 0xFF 0x7FF 352
- FCMPE(Z) 353
- Chapter 13 355
- Integration Test Registers 355
- Register (ITCTRL) 358
- Chapter 14 365
- • Dual issue on page 14-34 366
- Thumb instructions 369
- <Rn> 373
- 14.5 Media data-processing 374
- 14.7 Multiplies 376
- 14.8 Divide 378
- 14.9 Branches 379
- <addr_md_1cycle> 381
- <addr_md_3cycle> 381
- LDR R5, [R2, #4]! 382
- LDR R6, [R2, #0X10]! 383
- LDR R7, [R2, #0X20]! 383
- <addr_md_3cycle> 384
- RFEIA <Rn> 388
- SRSIA #<mode> 388
- MCR <cond> 390
- MRC <cond> 390
- 1- - - 392
- 14.23 Dual issue 398
- Chapter 15 401
- AC Characteristics 401
- 15.1 Processor timing 402
- Appendix A 414
- Processor Signal Descriptions 414
- A.2 Global signals 416
- A.3 Configuration signals 417
- A.5 L2 interface signals 421
- A.6 TCM interface signals 426
- A.8 Debug interface signals 430
- A.9 ETM interface signals 432
- A.10 Test signals 433
- A.11 MBIST signals 434
- A.12 Validation signals 435
- A.13 FPU signals 436
- Appendix B 437
- ECC Schemes 437
- Appendix C 439
- Revisions 439
- Glossary 442
- Write response channel (B) 444
- WT See Write-through 456
- Cache terminology diagram 456
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