IF/ELSE/ENDIF Example

IF/ELSE/ENDIF Example

Directives highlighted in this example are:

• if

else

endif

Program Functional Description

This program demonstrates the utility of IF, ELSE and ENDIF assembly directives.

Commented Code Listing

list p=16f877 ;Select the device.

#include <p16f877.inc> ;Include standard header file

;for the selected device.

variable config ;variable used to define

;required configuration of

;PORTA & PORTB

config set D'1'

RST CODE H'0' ;The code section named RST

;is placed at H'0'. The

;instruction 'goto start' is

;placed in code section RST

goto start ;Jumps to the location labelled

;'start'.

INTRT CODE H'4' ;The code section named INTRT is

;placed at H'4'. The instruction

;'goto service_int' is placed in

;code section INTRT.

goto service_int ;Jumps to the location labelled

;'service_int'.

PGM CODE ;This is the begining of the code

;section named PGM. It is a

;relocatable code section since

;no absolute address is given

;along with directive 'CODE'.

start

if config==H'0' ;If config==H'0' is true,

clrw ;assemble the mnemonics up to

movwf TRISA ;the directive 'else'.

movlw H'ff'

movwf TRISB

else

clrw ;If config==H'0' is false,

movwf TRISB ;assemble the mnemonics up to

movlw H'ff' ;the directive 'endif'.

movwf TRISA

endif

goto $

service_int

retfie

end