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MACHINE INSTRUCTION ENCODING AND DECODING
P:
0 =
do
not pop stack
1
= pop stack after operation
REG: register stack element
000 = stack top
001
= next on stack
010 = third stack element, etc.
Table
A-2
lists all 80287 machine instructions
in
binary sequence. This table may be used to "disassem-
ble"
instructions
in
unformatted memory dumps or instructions monitored from the data bus. Users
writing exception handlers may also find this information useful to identify the offending instruction.
Table A·2. Machine Instruction Decodin.9 Guide
1st
Byte
ASM286 Instruction
2nd Byte Bytes
3,4
Format
Hex
Binary
08
1101
1000
MOOOO
OR/M
(disp-Io),(disp-hi)
FAOO
short-real
08
1101
1000
MOOOO
1R/M
(disp-Io),(disp-hi) FMUL
short-real
08
1101
1000
M0001
OR/M
(disp-Io),(disp-hi) FCOM
short-real
08
1101
1000
M0001
1R/M
(disp-Io),(disp-hi)
FCOMP short-real
08
1101
1000
M0010
OR/M
(disp-Io),(disp-hi) FSUB
short-real
08
1101
1000
M0010
1R/M
(disp-Io),(disp-hi)
FSUBR short-real
08
1101
1000
M0011
OR/M
(disp-Io),(disp-hi)
FOIV
short-real
08
1101
1000
M0011
1R/M
(disp-Io),(disp-hi)
FOIVR short-real
08
1101
1000
1100
OREG
FAOO
ST,ST(i)
08
1101
1000
1100
1REG FMUL
ST,ST(i)
08
1101
1000
1101
OREG
FCOM ST(i)
08
1101
1000
1101
1REG
FCOMP ST(i)
08
1101
1000
1110
OREG
FSUB ST,ST(i)
08
1101
1000
1110
1REG
FSUBR
ST,ST(i)
08
1101
1000
1111
OREG
FOIV
ST,ST(i)
08
1101
1000
1111
1REG
FOIVR
ST,ST(i)
09
1101
1001
MOOOO
OR/M
(disp-Io),(disp-hi) FLO
short-real
09
1101
1001
MOOOO
1R/M
reserved
09
1101
1001
M0001
OR/M
(disp-Io),(disp-hi)
FST short-real
09
1101
1001
M0001
1R/M
(disp-Io),(disp-hi)
FSTP short-real
09
1101
1001
M0010
OR/M
(disp-Io),(disp-hi) FLOENV 14-bytes
09
1101
1001
M0010
1R/M
(disp-Io),(disp-hi) FLOCW
2-bytes
09
1101
1001
M0011
OR/M
(disp-Io),(disp-hi)
~
FSTENV 14-bytes
09
1101
1001
M0011
1R/M
(disp-Io),(disp-hi) FSTCW
2-bytes
09
1101
1001 1100
OREG
FLO
ST(i)
09
1101 1001
1100
1REG
FXCH
ST(i)
09
1101
1001
1101
0000
FNOP
09
1101
1001
1101
0001
reserved
09
1101 1001
1101
001-
reserved
09
1101
1001
1101
01--
reserved
D9
1101 1001
1101
1RFG
*(1
)
09
1101
1001
1110 0000
FCHS
09
1101
1001
1110
0001
FABS
09
1101 1001
1110 001·
reserved
09
1101
1001
1110
0100
FTST
09
1101
1001
1110
0101
FXAM
09
1101
1001
1110 011·
reserved
09
1101 1001
1110 1000
FL01
A-2