I am currently working on a small project using a PIC16F84A. I need to set up the 4-bit communication with the LCD but have not been able to get it to function. I was able to set up the 8-bit communication but the 4-bit still eludes me. At this point I am only trying to get the LCD to display a "T".

I have the following code, could someone tell me what I am doing wrong.

BCF STATUS,RP0
CLRF PORTA
CLRF PORTB
BSF STATUS,RP0
MOVLW 0X00
MOVWF TRISA
MOVLW 0X0F
MOVWF TRISB
BCF STATUS,RP0

CALL DELAY_20M
CALL DELAY_20M
CALL DELAY_20M
CALL DELAY_20M
CALL DELAY_20M

ORG 0X0200

BCF PORTA,RA0
CALL LCD_INIT_4_BIT
BSF PORTA,RA0
CLRW
MOVWF TEMP
DISPLAY
MOVF TEMP,W
INCF TEMP,F
CALL TEST
CALL LCD_4BIT_CONV
IORLW 0X00
BTFSC STATUS,Z
GOTO STOP
CALL TOGGLE_E
CALL DELAY_20M
GOTO DISPLAY
STOP GOTO $

;SUBROUTINES

LCD_INIT_4_BIT
BCF PORTA,RA0
MOVLW 0X20
CALL LCD_4BIT_CONV
MOVLW 0X20
CALL LCD_4BIT_CONV
MOVLW 0X20
CALL LCD_4BIT_CONV
MOVLW 0X28
CALL LCD_4BIT_CONV
MOVLW 0X0C
CALL LCD_4BIT_CONV
MOVLW 0X01
CALL LCD_4BIT_CONV
MOVLW 0X06
CALL LCD_4BIT_CONV
MOVLW 0X02
CALL LCD_4BIT_CONV
RETURN

LCD_4BIT_CONV

MOVWF TEMP2
SWAPF TEMP2,W
ANDLW 0X0F
MOVWF PORTB
BCF PORTA,RA0
CALL TOGGLE_E
CALL DELAY_20M
MOVF TEMP2,W
ANDLW 0X0F
MOVWF PORTB
BCF PORTA,RA0
CALL TOGGLE_E
CALL DELAY_20M
BSF PORTA,RA0
RETURN

TOGGLE_E
BSF PORTA,RA1
NOP
NOP
NOP
BCF PORTA,RA1
RETURN

DELAY_20M
MOVLW 0X03
MOVF DVAR
P151
MOVLW 0XF3
MOVWF DVAR1
P152
MOVLW 0X01
MOVWF DVAR2
P153
DECF DVAR2,F
BTFSS STATUS,Z
GOTO P153
DECF DVAR1,F
BTFSS STATUS,Z
GOTO P152
DECF DVAR,F
BTFSS STATUS,Z
GOTO P151
RETURN

TEST
ADDWF PCL,F
RETLW "T"
RETLW 0X00

END

I probably do not need to say this but I am kind of new to microcontrollers.

Thanks

 

Have you tried debugging in MPLAB SIM? Also your code is free for comments. Very hard for other people to help. Commenting will also help you in the coding process.