Intel 80287 User Manual

MACHINE INSTRUCTION ENCODING AND DECODING
Table A-2. Machine Instruction Decoding Guide (Cont'd.)
1st Byte
2nd Byte Bytes 3, 4
ASM286 Instruction
Hex
Binary
Format
DF 1101 1111 1100 1REG
*(7)
OF 1101 1111 1101 OREG
*(8)
OF 1101 1111 1101
1REG *(9)
OF 1101 1111 1110 000
FSTSWAX
OF 1101 1111
1111
XXX reserved
NOTE:
* The marked encodings are not generated by the language translators. If, however, the 80287 encounters
one of these encodings
in the instruction stream, it will execute it as follows:
(1) FSTP STeil
(2) FCOM STeil
(3) FCOMP STeil
(4) FXCH STeil
(5) FCOMP STeil
(6) FFREE STeil and pop stack
(7) FXCH STeil
(8) FSTP STeil
(9) FSTP STeil
A-5
pcjs.org

Intel 80287 Specifications

General

Brand	Intel
Model	80287
Category	Computer Hardware
Language	English