Data Movement Instructions

A Course in Microprocessor

Electrical Engineering Department

University of Indonesia

Assembler Detail Directives

– Some common assembly language directives (pseudo-operations) appear in Table 4.21

– Directives indicate how an operand or section of program is to be processed by the assembler:

• Storing Data in a Memory Segment: DB, DW, DD, SEGMENT, .DATA, ENDS, DUP, ALIGN -ex.4.12

• ASSUME, EQU, ORG: the EQU equates a numeric, ASCII, or LABEL to another label -ex.4.13; the THIS refers the data as byte or word -ex.4.14; the ORG (origin) changes the starting offset address of data in the data segment; the ASSUME tells the

Assembler Detail (cont’d)

the assembler what names have been chosen for the code, data, extra, and stack segments; the PROC and ENDP indicate the start and end of a procedure (subroutine) -ex.4.15; others are CALLF, CALLN, RETF, RETN, NEAR, FAR -ex.4.16

Memory Organization– The assembler uses two basic formats for deve-loping

software: models and full-segment defi-nitions (available to the MASM assembler)

– Models (ex.4.17): The TINY model (64 KB) and the SMALL model (128 KB), and HUGE model (>128 KB)

Assembler Detail (cont’d)

Full Segment Definitions– Ex.4.18 & Ex.4.19 illustrate the use of full-

segment definitions• Full-segment definitions are also used with the

Borland and Microsoft C/C++ environments for procedures developed in assembly language

– More structured form than the model method– STACK_SEG, DAT_SEG, CODE_SEG, END

MAIN

Assembler Detail (cont’d)

A Sample Program– Study carefully Ex.4.20