Chapter 2. Programming Model
2-59
Instruction Set Summary
See Appendix F, òSimpliTed Mnemonics,ó in
The Programming Environments Manual
for
a complete set of simpliTed mnemonics.
2.3.4.5 System Linkage InstructionUISA
The System Call (
sc
) instruction permits a program to call on the system to perform a
service; see Table 2-42 and also Section 2.3.6.1, òSystem Linkage InstructionsOEA,ó for
additional information.
Executing this instruction causes the system call exception handler to be evoked. For more
information, see Section 4.6.10, òSystem Call Exception (0x00C00).ó
2.3.4.6 Processor Control InstructionsUISA
Processor control instructions are used to read from and write to the condition register
(CR), machine state register (MSR), and special-purpose registers (SPRs). See
Section 2.3.5.1, òProcessor Control InstructionsVEA,ó for the
mftb
instruction and
Section 2.3.6.2, òProcessor Control InstructionsOEA,ó
for information about the
instructions used for reading from and writing to the MSR and SPRs.
2.3.4.6.1 Move to/from Condition Register Instructions
Table 2-43 summarizes the instructions for reading from or writing to the condition register.
Implementation Note
The PowerPC architecture indicates that in some implementations
the Move to Condition Register Fields (
mtcrf
) instruction can perform more slowly when
only a portion of the Telds are updated as opposed to all of the Telds. The condition register
access latency for the MPC7400 is the same in both cases.
Table 2-41. Trap Instructions
Name
Mnemonic
Syntax
Trap Word Immediate
twi
TO
,r
A
,
SIMM
Trap Word
tw
TO
,r
A
,r
B
Table 2-42. System Linkage InstructionUISA
Name
Mnemonic
Syntax
System Call
sc
Table 2-43. Move to/from Condition Register Instructions
Name
Mnemonic
Syntax
Move to Condition Register Fields
mtcrf
CRM
,r
S
Move to Condition Register from XER
mcrxr
crf
D
Move from Condition Register
mfcr
r
D