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TI486 Microprocessor - Al Kossow's Bitsavers

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Instruction Fields<br />

Table 7-7. mod rim Field Encoding Dependent on w Field<br />

16-BIT 16-BIT 32-BIT 32-BIT<br />

mod rIm OPERATION OPERATION OPERATION OPERATION<br />

w=o w=1 w=o w=1<br />

11 000 AL AX AL EAX<br />

11 001 CL CX CL ECX<br />

11 010 DL DX OL EDX<br />

11 011 BL BX BL EBX<br />

11100 AH SP AH ESP<br />

11 101 CH BP CH EBP<br />

11 110 DH SI OH ESI<br />

11 111 BH 01 BH EDI<br />

7.2.7 mod and base Fields<br />

In Table 7-7, the note "s-i-b present" for certain entries forces the use of the<br />

mod and base field as listed in Table 7-8.<br />

Table 7-8. mod base Field Encoding<br />

mod rIm<br />

32-BIT ADDRESS MODE<br />

WITH mod rIm BYTE AND<br />

NO s-i-b BYTE PRESENT<br />

00000 OS:[EAX+(scaled index)]<br />

00001 DS:[ECX+(scaled index)]<br />

00010 DS:[EDX+(scaled index)]<br />

00011 OS:[EBX+(scaled index)]<br />

00100 SS:[ESP+(scaled index)]<br />

00101 DS:[d32+(scaled index)]<br />

00110 OS:[ESI+(scaled index)]<br />

00111 OS:[EOI+(scaled index)]<br />

01000 DS:[EAX+(scaled index)+d8]<br />

01 001 DS:[ECX+(scaled index)+d8]<br />

01 010 OS:[EOX+(scaled index)+d8]<br />

01 011 DS:[EBX+(scaled index)+d8]<br />

01100 SS:[ESP+(scaled index)+d8]<br />

01 101 SS:[EBP+(scaled index)+d8]<br />

01 110 OS:[ESI+(scaled index)+d8]<br />

01 111 OS:[EOI+(scaled index)+d8]<br />

10000 DS:[EAX+(scaled index)+d32]<br />

10001 DS:[ECX+(scaled index)+d32]<br />

10010 DS:[EDX+(scaled index)+d32]<br />

10011 DS:[EBX+(scaled index)+d32]<br />

10100 SS:[ESP+(scaled index)+d32]<br />

10101 SS:[EBP+(scaled index)+d32]<br />

10110 DS:[ESI+(scaled index)+d32]<br />

10111 DS:[EDI+(scaled index)+d32]<br />

7-9

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