Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 160

MPC8xx Core Register Set
Description
General-purpose
registers
Condition register
Table 4-2 lists SPRs defined by the PowerPC architecture implemented on the MPC885.
SPR Number
Decimal SPR [5–9] SPR [0–4]
1 00000
8 00000
9 00000
268 01000
269 01000
1
Extended opcode for mftb, 371 rather than 339.
2
Any write (mtspr) to this address causes an implementation-dependent software emulation exception.
4.1.1.1 PowerPC User-Level Register Bit Assignments
This section describes bit assignments of PowerPC registers implemented by the MPC885. For more
details, see the Programming Environments Manual for 32-Bit Processors.
4.1.1.1.1 Condition Register (
The condition register (CR) is a 32-bit register that reflects the result of certain operations and provides a
mechanism for testing and branching. The bits in the CR are grouped into eight 4-bit fields, CR0–CR7, as
shown in Figure 4-1.
CR0 CR1
0 3 4
The CR fields can be set in one of the following ways:
• Specified fields of the CR can be set from a GPR by using the mtcrf instruction.
• An mcrf instruction can move the contents of XER[0–3] to a CR field.
• An mcrxr instruction can copy a specified XER field to a specified CR field.
4-2
Table 4-1. User-Level PowerPC Registers
Name Reference/Section
GPRs The thirty-two 32-bit (GPRs) are used for source
and destination operands.
CR See Section 4.1.1.1.1, "Condition Register (CR)."
Table 4-2. MPC885-Specific User-Level SPRs
Name Reference/Section
00001 XER See
"XER."
See the Programming
01000 LR
Environments Manual
01001 CTR See the Programming
Environments Manual
1
01100 TBL read Section 10.9,
"Timebase"
2
01101 TBU read
CR)
CR2 CR3
7 8 11 12
Figure 4-1. Condition Register (CR)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Access Level Serialize Access
Section 4.1.1.1.3, Write: Full sync
Read: Sync relative to load/store
operations
No
No
Write (as a store)
CR4 CR5
15 16 19 20 23
User —
User Only mtcrf
Serialize Access
CR6 CR7
24 27 28 31
Freescale Semiconductor