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User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
Page 6 of 377
750gx_umTOC.fm.(1.2)
March 27, 2006
4.2 Exception Recognition and Priorities ............................................................................................. 153
4.3 Exception Processing .................................................................................................................... 156
4.3.1 Machine Status Save/Restore Register 0 (SRR0) ............................................................... 156
4.3.2 Machine Status Save/Restore Register 1 (SRR1) ............................................................... 157
4.3.3 Machine State Register (MSR) ............................................................................................ 158
4.3.4 Enabling and Disabling Exceptions ...................................................................................... 160
4.3.5 Steps for Exception Processing ........................................................................................... 160
4.3.6 Setting MSR[RI] ................................................................................................................... 161
4.3.7 Returning from an Exception Handler .................................................................................. 161
4.4 Process Switching ......................................................................................................................... 162
4.5 Exception Definitions ..................................................................................................................... 162
4.5.1 System Reset Exception (0x00100) ..................................................................................... 163
4.5.1.1 Soft Reset ..................................................................................................................... 164
4.5.1.2 Hard Reset ................................................................................................................... 164
4.5.2 Machine-Check Exception (0x00200) .................................................................................. 167
4.5.2.1 Machine-Check Exception Enabled (MSR[ME] = 1) ..................................................... 168
4.5.2.2 Checkstop State (MSR[ME] = 0) .................................................................................. 169
4.5.3 DSI Exception (0x00300) ..................................................................................................... 169
4.5.4 ISI Exception (0x00400) ....................................................................................................... 169
4.5.5 External Interrupt Exception (0x00500) ............................................................................... 169
4.5.6 Alignment Exception (0x00600) ........................................................................................... 170
4.5.7 Program Exception (0x00700) ............................................................................................. 170
4.5.8 Floating-Point Unavailable Exception (0x00800) ................................................................. 171
4.5.9 Decrementer Exception (0x00900) ...................................................................................... 171
4.5.10 System Call Exception (0x00C00) ..................................................................................... 171
4.5.11 Trace Exception (0x00D00) ............................................................................................... 171
4.5.12 Floating-Point Assist Exception (0x00E00) ........................................................................ 171
4.5.13 Performance-Monitor Interrupt (0x00F00) ......................................................................... 172
4.5.14 Instruction Address Breakpoint Exception (0x01300) ........................................................ 173
4.5.15 System Management Interrupt (0x01400) ......................................................................... 173
4.5.16 Thermal-Management Interrupt Exception (0x01700) ....................................................... 174
4.5.17 Data Address Breakpoint Exception .................................................................................. 175
4.5.17.1 Data Address Breakpoint Register (DABR) ................................................................ 175
4.5.18 Soft Stops .......................................................................................................................... 175
4.5.19 Exception Latencies ........................................................................................................... 176
4.5.20 Summary of Front-End Exception Handling ....................................................................... 176
4.5.21 Timer Facilities ................................................................................................................... 177
4.5.22 External Access Instructions .............................................................................................. 177
5. Memory Management .............................................................................................. 179
5.1 MMU Overview .............................................................................................................................. 179
5.1.1 Memory Addressing ............................................................................................................. 181
5.1.2 MMU Organization ............................................................................................................... 181
5.1.3 Address-Translation Mechanisms ........................................................................................ 186
5.1.4 Memory-Protection Facilities ................................................................................................ 187
5.1.5 Page History Information ..................................................................................................... 188
5.1.6 General Flow of MMU Address Translation ......................................................................... 189
5.1.6.1 Real-Addressing Mode and Block-Address-Translation Selection ............................... 189
5.1.6.2 Page-Address-Translation Selection ............................................................................ 190
5.1.7 MMU Exceptions Summary ................................................................................................. 192