4bit.asm

Library for the 8051 microcontroller. such as math routine, hexBCD, LCD, Keyboard, I2C, Remote, Ke

;------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
;Author: Ashwin.V
;Country:India
;Code:LCD interface in 4bit mode
;CPU:At89c51@11.0592Mhz
;Tips:All you need to do is call the line where you want to display the message, mov the charecter to lcd_data and call datw.
;If you want to display a string, move the address of the hardcodded string into dptr and call datw.
;-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------		
			
	             RS 		    EQU 	p3.7
		         RW             EQU     p3.6
				 En  		    EQU	    p3.5
				 LCD_DATA	    DATA	30h


org 0000h
  
  ljmp lcd4_main

org 0030h


;___________________________________________________________________________
;---------------------delay subroutines start here--------------------------
;___________________________________________________________________________

;-------------------------------8us delay-----------------------------------
delay_8us:         nop
				   nop
				   nop
				   nop
				   nop
				   nop
				   ret 
;------------------------------100us delay----------------------------------

delay_100us:       push 00
                   mov r0,#46
delay_100us_loop:  djnz r1,delay_100us_loop
                   pop 00
                   ret

;------------------------------16ms delay-----------------------------------

delay_16ms:         push 00
                    push 01
                    mov r0,#30
delay_16ms_loop1:   mov r1,#255
delay_16ms_loop2:   djnz r1,delay_16ms_loop2
                    djnz r0,delay_16ms_loop1 
                    pop 01
                    pop 00
                    ret

;--------------------------half second delay-------------------------------

delay_half_second:	push 00
			        push 01
			        push 02
	                mov r2,#0ah 
delay_half_second1:	mov r1,#64h
delay_half_second2:	mov r0,#0ffh
back:	        	djnz r0,back
	       		    djnz r1, delay_half_second2
		            djnz r2,delay_half_second1
			        pop 02
			        pop 01
			        pop 00
			        ret	   	  


;___________________________________________________________________________
;---------------------delay subroutines end here----------------------------
;___________________________________________________________________________


;___________________________________________________________________________
;----------------------LCD subroutines start here---------------------------
;___________________________________________________________________________

;-----------------------------------------------------------------
;----------------message definition and display-------------------
;----------------------------------------------------------------- 


disp_LCD_message:     push acc
                      push 00h
                      mov r0,#17

disp_LCD_message1:    mov a, #00h	; reset accumulator	
		              movc a,@a+dptr
					  mov lcd_data,a
                      acall datw
		              inc dptr
					  djnz r0,disp_LCD_message1

					  pop 00h
					  pop acc
					  ret

disp_testing:      DB "Testing 4bit LCD"
disp_initialising: DB "Initialising...."
disp_ready:        DB " 4bit LCD ready "
disp_clear:        DB "                "	   	


;-----------------------------------------------------------------
;----------------lcd initialisation starts here-------------------
;----------------------------------------------------------------- 

entry_set_mode:
  
        mov lcd_data,#00h	
		acall cmdw4
		acall delay_100us
		ret
;-----------------------------------------------------
;-----------------------------------------------------
lcd4_initialise:

		acall delay_16ms    ; wait for more than 15ms after vdd reaches 4.5v

		mov lcd_data,#020h	; 4bit interface
		acall cmdw4
		acall delay_100us
;-----------------------------------------------------
		mov lcd_data,#20h	; entry mode set
		acall cmdw4
		acall delay_100us

		mov lcd_data,#0c0h	; 2line 5x10 matrix
		acall cmdw4
		acall delay_100us
;------------------------------------------------------
		acall entry_set_mode

		mov lcd_data,#80h	; display off
		acall cmdw4
		acall delay_100us
;-------------------------------------------------------
		acall entry_set_mode

		mov lcd_data,#10h	; clear display
		acall cmdw4
		acall delay_100us
;--------------------------------------------------------
		acall entry_set_mode

		mov lcd_data,#60h	; cursor moves right, display doesn't shift
		acall cmdw4
		acall delay_100us
;--------------------------------------------------------
		acall entry_set_mode
				
		mov lcd_data,#0f0h	; cursor on and blink
		acall cmdw4
		acall delay_100us
				 
		ret

;-----------------------------------------------------------------
;-----------------lcd initialisation ends here--------------------
;----------------------------------------------------------------- 


;-----------------------------------------------------------------
;--------command and data write subroutines starts here-----------
;-----------------------------------------------------------------

;-------------------------------------------------
;--------------4bit command write-----------------
;-------------------------------------------------

cmdw4:
		push acc	
		clr RS
		clr En
				
		acall write_port
;--------------wait 8 machine cycles-------------
		acall delay_8us
;------------------------------------------------
		setb En
    	clr En		

		pop acc		
		ret

;------------------------------------------------
;--------------8bit command write----------------
;------------------------------------------------

cmdw:
		push acc	
		clr RS
		clr En

		acall write_port
;--------------wait 8 machine cycles-------------
		acall delay_8us	
;------------------------------------------------  
		setb En
		clr En
;-------------wait 8 machine cycles-------------				
    	acall delay_8us
;------------------------------------------------
		acall write_port
;--------------wait 8 machine cycles-------------
		acall delay_8us
;------------------------------------------------
		setb En
		clr En		

		pop acc	
		ret

;-------------------------------------------------
;----------------8bit data write------------------
;-------------------------------------------------

datw:	push acc
	   	setb RS
		clr En
		acall write_port
;--------------wait 8 machine cycles-------------
		acall delay_8us	
;------------------------------------------------		  
		setb En
		clr En
;-------------wait 8 machine cycles--------------				
        acall delay_8us
;------------------------------------------------
		acall write_port
;--------------wait 8 machine cycles-------------
		acall delay_8us	
;------------------------------------------------
		setb En
		clr En
				
		pop acc
		ret

;-------------------------------------------------
;----------------4bit port write------------------
;-------------------------------------------------

write_port:	
        mov a, lcd_data
		 
		rlc a
		mov p1.0, c	       ;D7
		rlc a
		mov p1.1, c	       ;D6
		rlc a
		mov p1.2, c	       ;D5
		rlc a
		mov p1.3, c	       ;D4

		mov lcd_data, a
		ret


;-------------------------------------------------------------
;--------command and data write subroutine ends here----------
;-------------------------------------------------------------


;--------------------------------------------------
;--------lcd line select(1/2) starts here----------
;--------------------------------------------------


line1:       mov lcd_data,#80h	     ;initial positio of cursor
             acall cmdw
			 acall delay_100us
			 ret

line2:       mov lcd_data,#0c0h	     ;initial position of cursor
             acall cmdw
			 acall delay_100us
			 ret

;--------------------------------------------------
;---------lcd line select(1/2) ends here-----------
;--------------------------------------------------

;___________________________________________________________________________
;-----------------------LCD subroutines ends here---------------------------
;___________________________________________________________________________

;__________________________________________________
;-----------------main code------------------
;__________________________________________________


lcd4_main:	mov p1, #00h
            clr En
		    clr RS
			clr rw
            mov IE,#00h

		    acall lcd4_initialise
;---------------------------------------------------------
lcd4_main1: lcall line1
			mov dptr,#disp_initialising
			acall disp_LCD_message
			acall delay_half_second
			acall delay_half_second
			acall delay_half_second
			acall delay_half_second

			lcall line1
			mov dptr,#disp_testing
			acall disp_LCD_message
			acall delay_half_second
			acall delay_half_second

			lcall line2
			mov dptr,#disp_ready
			acall disp_LCD_message
			acall delay_half_second
			acall delay_half_second
			acall delay_half_second
			acall delay_half_second

            sjmp lcd4_main1
			



end