Intel 210200-002 manual Direct Addressing

ARCHITECTURE AND INSTRUCTIONS

FIRST OPERAND CHOICE DEPENDS ON ADDRESSING MODE:'

	FIRST OPERAND IN MEMORY
INDIRECT ADDRj:SSING		DIRECT ADDRESSING
00';DISP = 0		MOD = 00
MOD=01	; OISP = DISP-LO SIGN	AND
	EXTENDED	R/M = 110
10 ; DISP = DISP-HI; DISP-LO		OPERAND EFFECTIVE
	OPERAND	"ADDRESS =
RIM:	EFFECTIVE ADDRESS	DISP-HI, DISP-LO

000(BX) + (SI) + DISP

001(BX) + (DI) + DISP

010(BP) + (SI) + DISP

011(BP) + (DI) + DISP

100(SI) + DISP

101 (DI) + DISP

i110 (BP) + DISP

-, 111 (BX) + DISP

,

Where ( ) means "contents of" 'Exception-directaddressing mode

Figure 2-5. Determining First Operand

FIRST OPERAND

IN REGISTER

	MOD = 11
	REGISTER
RIM:	'8-BIT	16-BIT
	(W = 0)	(W = 1)'
000	AL	AX
001	CL	CX
010	DL	DX
011	BL	BX
100	AH	SP
101	CH	BP
110	DH	SI
111	BH '	DI

,DATA

STRUCTURE

SIMPLE VARIABLE

ARRAYS

ARRAYS

OF RECORDS

DATA MEMORY		STACK
,WITHOUT BASE	WITH BASE
DIRECT	BX +: OFFSET	BP + OFFSET
SI	BX + SI	BP -+-SI
DI	BX + DI	BP + DI,
SI + OFFSET	BX + SI + OFFSET	BP + SI+ OFFSET
DI + OFFSET	BX + DI +: 9FFSET	BP + DI + OFFSET

Figure 2~6. Effective Addresses Used with Different Data Structures'

TYPE OF MEMORY REFERENCE	DEFAULT	ALTERNATE	LOGICAL ADDRESS
	SEGMENT	SEGMENT
	BASE	BASE
Instruction Fetch	CS	NONE.	IP
Stack Operation	SS	NONE	SP
String, Source	DS	CS,ES,SS	SI
String Destination	ES	NONE	DI
BP Used As Base Register	SS	CS,DS,ES	Effective Address
General Data Read/Write	DS	CS,ES,SS	Effective Address
Figure 2-7. 8088 Address Components

2-7