I am trying to interface with a LCD which uses the HD44780 interface.  I am
using a PIC16f73.  I am trying to use the LCD in 4bit mode connected to
PORTC.  I am currently just getting a blank screen.  I have put my code
below.  Can anybody see where I have gone wrong or suggest anything I can
try please?

include "p16f73.inc"

 CBLOCK	0x020
	R_DEL1
	R_DEL2
	R_WDATA_TMP1
	R_WDATA_TMP2
	R_SEND_W_TMP
	RAM_PORTC
	R_BIT
 endc

 org 0
	goto init

 org 4

init
	movlw	0xFF
	call	delay

	bsf		STATUS, RP0
	movlw	0x000
	movwf	TRISC
	bcf		OPTION_REG,5
	bcf		STATUS, RP0
	clrf	PORTC
	;bcf		PORTC, 4
	movlw	0x004
	call	clear_PORTC_bit
	
	
	movlw	0x003
	call	w_to_data
	call	pulse_e
	movlw	0x00A
	call	delay

	movlw	0x003
	call	w_to_data
	call	pulse_e
	movlw	0x004
	call	delay

	movlw	0x003
	call	w_to_data
	call	pulse_e
	movlw	0x004
	call	delay

	movlw	0x002
	call	w_to_data
	call	pulse_e
	movlw	0x004
	call	delay

	movlw	b'00101000';interface length
	call	send_w
	call	delay_1ms
	call	delay_1ms
	
	movlw	b'00000010'
	call	send_w
	call	delay_1ms
	call	delay_1ms
	movlw	b'00010000'
	call	send_w
	call	delay_1ms
	call	delay_1ms

	movlw	b'00000110' ;Cursor Direction
	call	send_w
	call	delay_1ms
	call	delay_1ms
	
	movlw	b'00001111'
	call	send_w
	call	delay_1ms
	call	delay_1ms
	
mainloop
	;bcf		PORTC, 4
	movlw	0x004
	call	clear_PORTC_bit
	movlw	b'00000010'
	call	send_w
	;bsf		PORTC, 4
	movlw	0x004
	call	set_PORTC_bit
	call	delay_1ms
	
	movlw 'H'
	call	send_w
	
	goto mainloop
	

pulse_e
	;bsf		PORTC, 5
	movlw	0x005
	call	set_PORTC_bit
	nop
	nop
	nop
	nop
	;bcf		PORTC, 5
	movlw	0x005
	call	clear_PORTC_bit
	call	delay_1ms
	call	delay_1ms
	return

; Calls the delay_1ms routine the number of times specified by
; the W register.
delay
	movwf	R_DEL2
delay_loop
	call	delay_1ms
	decfsz	R_DEL2, F
		goto	delay_loop
	return
	
; When called gives a delay of about 1000 cycles, or 1ms at 4Mhz
; before the next instruction is executed.
delay_1ms
	movlw	d'248'
	movwf	R_DEL1
delay_1ms_loop
	nop
	decfsz	R_DEL1, F
		goto	delay_1ms_loop
	return

send_w
	movwf	R_SEND_W_TMP
	swapf	R_SEND_W_TMP, F
	movlw	0x0F
	andwf	R_SEND_W_TMP, W
	call	w_to_data
	call	pulse_e
	
	swapf	R_SEND_W_TMP, F
	movlw	0x0F
	andwf	R_SEND_W_TMP, W
	call	w_to_data
	call	pulse_e
	return

w_to_data
	movwf	R_WDATA_TMP1
	movf	PORTC, W
	movwf	R_WDATA_TMP2
	bcf		R_WDATA_TMP2, 0
	bcf		R_WDATA_TMP2, 1
	bcf		R_WDATA_TMP2, 2
	bcf		R_WDATA_TMP2, 3
	btfsc	R_WDATA_TMP1, 0
		bsf		R_WDATA_TMP2, 0
	btfsc	R_WDATA_TMP1, 1
		bsf		R_WDATA_TMP2, 1
	btfsc	R_WDATA_TMP1, 2
		bsf		R_WDATA_TMP2, 2
	btfsc	R_WDATA_TMP1, 3
		bsf		R_WDATA_TMP2, 3
	movf	R_WDATA_TMP2, W
	movwf	PORTC
	
	return

clear_PORTC_bit
	movwf	R_BIT
	movfw	PORTC
	movwf	RAM_PORTC
	bcf		RAM_PORTC, R_BIT
	movfw	RAM_PORTC
	movwf	PORTC
	
	return

set_PORTC_bit
	movwf	R_BIT
	movfw	PORTC
	movwf	RAM_PORTC
	bsf		RAM_PORTC, R_BIT
	movfw	RAM_PORTC
	movwf	PORTC

	return

 end


Stewart Abel

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