Instruction format for IBM 8088 
Author Message
 Instruction format for IBM 8088

Could someone possibly explain how the 8088 decodes instructions? I find it
quite difficult to decifer. I know there is an opcode byte, a mod,reg,r/m
byte and displacements, but what really bothers me is the mod,reg,r/m byte.
Is there some connection between all the instructions that I fail to see?
It's just a mess if you look at it. 109 instructions and some 30-40 different
formats for every one? I'd hate to write a de{*filter*}. It would be slow if I
did.


Tue, 22 Nov 1994 18:25:06 GMT  
 Instruction format for IBM 8088
Of course, i can always include my address, too.



Wed, 23 Nov 1994 14:56:27 GMT  
 Instruction format for IBM 8088

Quote:
>Could someone possibly explain how the 8088 decodes instructions? I find it
>quite difficult to decifer. I know there is an opcode byte, a mod,reg,r/m
>byte and displacements, but what really bothers me is the mod,reg,r/m byte.
>Is there some connection between all the instructions that I fail to see?
>It's just a mess if you look at it. 109 instructions and some 30-40 different
>formats for every one? I'd hate to write a de{*filter*}. It would be slow if I
>did.

No problem. for starters, the Turbo Assembler Quick Reference guide explains
it very nicely. unfortunately, there are several charts to follow, involving
effective addressing and the modr/m values. send mail to me if you do not have
the turbo assembler package and i will get back to you with the tables.


Wed, 23 Nov 1994 14:39:26 GMT  
 
 [ 3 post ] 

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