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User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
gx_02.fm.(1.2)
March 27, 2006
Programming Model
Page 111 of 377
TBL
2
268 01000 01100 User (VEA) mfspr
284 01000 11100 Supervisor (OEA) mtspr
TBU
2
269 01000 01101 User (VEA) mfspr
285 01000 11101 Supervisor (OEA) mtspr
XER 1 00000 00001 User (UISA) Both
Table 2-33. PowerPC Encodings (Page 3 of 3)
Register Name
SPR
1
Access mfspr/mtspr
Decimal SPR[5–9] SPR[0–4]
Note:
1. The order of the two 5-bit halves of the SPR number is reversed compared with actual instruction coding. For mtspr and mfspr
instructions, the SPR number coded in assembly language does not appear directly as a 10-bit binary number in the instruction.
The number coded is split into two 5-bit halves that are reversed in the instruction, with the high-order five bits appearing in bits
16–20 of the instruction and the low-order five bits in bits 11–15.
2. The TB Registers are referred to as TBRs rather than SPRs and can be written to using the mtspr instruction in supervisor mode
and the TBR numbers here. The TB Registers can be read in user mode using either the mftb or mfspr instruction and specifying
TBR 268 for TBL and SPR 269 for TBU.