Flash1 - Output and nested time delay

The main program can be broken up into three main areas:

Start - This part of the program sets up the Input Output Ports. Note that all bits of Port B are set to be outputs except the least significant bit. This is accomplished by sending the byte 00000001 (binary) to TRISB. To select TRISB, STATUS must first be set and then reset. This is because of the dual bank register system in this microprocessor.
Again - This is the beginning of the main loop. The program puts out a sequence of HIs and LOs to PORTB (refer to the comments). Note that the second and third bits from the right are the only bits that make a difference here, the rest are just 0 anyway. The Call to Delay, inserts a time delay, otherwise the lights would flash faster than the eye can see.
Delay - This is a nested loop. First Loop1 is loaded with Hex 20 (Decimal 32). Then Loop2 is loaded with Hex FF (Decimal 255). Then Loop2 is decremented to 0 and reset to 255 for each value of Loop1. The total number of loops is thus 255x32 = 8160.


;**************************************************************************
;
; This Program developed by Peter Hayles for PIC 16C711
;
; Flashes the LEDs on B1 and B2.
; The LEDs should be connected from B1 and B2 to ground
; with a 100 ohm resistor in series .
;
;**************************************************************************

#include 	"p16c711.inc"
        	LIST P=16C711

;--------------------------------------------------------------------------
; Variables
;--------------------------------------------------------------------------

RAM		EQU	0x30	

Portin		EQU     RAM+0
Loop1       	EQU    	RAM+1
Loop2	      	EQU    	RAM+2
Loop		EQU  	RAM+3


;--------------------------------------------------------------------------
; Program Code
;--------------------------------------------------------------------------

            	ORG     0       
            	GOTO   	Start

;--------------------------------------------------------------------------
; Main Program
;--------------------------------------------------------------------------

            	ORG     H'05'

Start
		BCF	STATUS,RP0	;Clear Data Bus
		CLRF	PORTB
		CLRF	PORTA		
		BSF	STATUS,RP0	;Set Port B 0=Input & 1-7=Output
		MOVLW	B'00000001'	
		MOVWF	TRISB		
		BCF	STATUS,RP0	;Clear Data Bus

Again		
		
		MOVLW	B'00000110'	;Set Outputs to HI, HI
		MOVWF	PORTB
		Call	Delay

		MOVLW	B'00000100'	;Set Outputs to HI, LO
		MOVWF	PORTB
		Call	Delay

		MOVLW	B'00000010'	;Set Outputs to LO, HI
		MOVWF	PORTB
		Call	Delay

		MOVLW	B'00000100'	;Set Outputs to HI, LO
		MOVWF	PORTB
		Call	Delay

		MOVLW	B'00000010'	;Set Outputs to LO, HI
		MOVWF	PORTB
		Call	Delay

		MOVLW	B'00000100'	;Set Outputs to HI, LO
		MOVWF	PORTB
		Call	Delay

		MOVLW	B'00000010'	;Set Outputs to LO, HI
		MOVWF	PORTB
		Call	Delay

		GOTO	Again

; This routine is two nested delays

Delay		MOVLW	H'20'
		MOVWF	Loop1
More1		MOVLW	H'FF'
		MOVWF	Loop2		
More2		NOP
		DECFSZ	Loop2,F
		GOTO	More2		
		DECFSZ	Loop1,F
		GOTO	More1
		RETLW	0

		END

Contacts:

Email Peter Hayles, Author