4.7 INSTRUCTION ENCODING DETAILS
The following paragraphs provide the details of the object code formats for the general,
branch, set on condition, save, and restore type coprocessor instructions.
All FPCP instructions are from two to eight words in length as shown below (the longest
case is for an immediate operand of six words --the X or P format).
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
OPERATION WORD
MC68881 COMMAND WORD, OR CONDITIONAL PREDICATE
EFFECTIVE ADDRESS EXTENSION WORDS, DISPLACEMENT, OR IMMEDIATE 0PERAND (IF ANY, 1-6 WORDS)
All FPCP instructions begin with an operation word, formatted as follows:
'15 14 '13 ]2 11 10 9 8 7 6 5 4 3 2 'i 0
I , I., I , J, I CDPROCESSOR,O I 0 I 0 I 0 I ( .PEOE ENOENT
Coprocessor ID -- Specifies which coprocessor in the system is to execute this in-
struction. Freescale assemblers default to ID= 1 for the FPCP.
Type -- Specifies the type of coprocessor instruction:
000- General Instructions (Arithmetics, FMOVE, FMOVEM)
001 -- FDBcc, FScc, FTRAPcc
010- FBcc.W
011 -- FBcc.L
100 -- FSAVE
101 -- FRESTORE
110 -- (Undefined, Reserved)
111 m (Undefined, Reserved)
Type Dependent m Normally specifies the effective address or conditional predicate,
but usage depends on the type field.
4.7.1 General Type Coprocessor Instruction Format
The general type coprocessor instruction format (shown below) is used for all FPCP arith-
metic, move, move multiple, move constant, and transcendental instructions.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
OPERATION WORD
EFFECTIVE ADDRESS
MODE I REGISTER
COMMAND WORD
OPCLASS RX I RY I EXTENSION
The interpretation of the command word fields, OPCLASS, RX, RY, and EXTENSION field
varies with the instruction type and is summarized in Table 4-11.
MC68881/MC68882 USER'S MANUAL
FREESCALE
4-125
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