OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE

Encoded

in the

Instruction

Explicit

in the

Instruction

Assumed Unless

Overridden

by Prefix

Single Index

BX

or

BP

or

SI

or

DI

+

+

 

Double Index

BX

SI

or

or

BP

DI

 

+

Displacement + EffectiveAddress

CS 0000

or

SS0000

or

DS

0000

 

 

or

 

ES

0000

+

Physical Addr

EU

BIU

A1015-0A

Figure 2-12. Memory Address Computation

The displacement is an 8- or 16-bit number contained in the instruction. The displacement gen- erally is derived from the position of the operand’s name (a variable or label) in the program. The programmer can modify this value or explicitly specify the displacement.

2-29

Page 58
Image 58
Intel 80C188XL, 80C186XL user manual Physical Addr, Biu