;*********************************************************************
;THIS CODE WILL DISPAY A CHARACTER "G" ON LCD AND SINK THE CHAR DOWNWARDS
;*********************************************************************


        .org 0000h
;*********************************************************************
;PORT DEFINED (CAN BE MODIFIED ACCORING TO CIRCUIT
;*********************************************************************
        ;p0= d0-d7
        ;RS  rs=0 for command    rs=1 for data
        ;RW  wr=0 for write      wr=1 for read
        ;EN   enable  -\_     
         .equ RS, p3.5
         .equ RW, p3.4
         .equ EN, p3.3
;*********************************************************************
;TO INITIALIZE THE LCD
;*********************************************************************

        mov a,#38h     ;2 line 5x7
        acall command
        mov a,#0ch     ;lcd on cursor on
        acall command
        mov a,#01h     ;clr lcd
        acall command
        mov a,#06h     ;shift cursor right
        acall command

        mov a,#'a'     ; testing for "a"
        acall ddisp

        acall delay
        acall writech   ;writes char in CG ram of lcd

        mov a,#80h      ;go to start of lcd
        acall command
        mov a,#01h
        acall command   ;clr disp

;*********************************************************************
;LOOP FOR DISPLAYING 8 ROW (1CHAR) STORED IN CG RAM
;*********************************************************************

s:
        mov r0,#00h     ;CGram address
again1: mov a,#85h      ;DDRAM addres display position on lcd 
        acall command
        acall delay
        mov a,r0        ; r0=0 means first char of cg ram
        acall ddisp     ; display on lcd
        inc r0          ; inc counter
        cjne r0,#08h,again1

        sjmp s          ; main loop reapet


command:acall ready      ;chk lcd is ready to accept command
        mov p0,a
        clr RS  ;rs=0 for command
        clr RW  ;wr=0 for write
        setb EN
        clr EN
        ret

ddisp:  acall ready
        mov p0,a
        setb RS  ;rs=1 for data
        clr RW  ;wr=0 for write
        setb EN
        clr EN
        ret

ready:  setb p0.7
        clr RS    ;rs=0 command
        setb RW   ;wr=1 read
back:   clr EN    ;enable
        setb EN
        jb p0.7,back        
        ret

delay:  mov r7,#99h
w2:     mov r6,#00h
w1:     djnz r6,w1
        djnz r7,w2
        ret

writech:acall ready     
        mov a,#40h     ; go to 00 of cgram
        mov p0,a
        clr RW
        clr RS
        setb EN
        clr EN


        mov r7,#64      ;counter for 64 times  8pix hor  x  8lines = 1 char
        mov dptr,#tabel ;load address values of tabel
wr1:    clr a
        acall ready
        movc a,@a+dptr
        mov p0,a         ; this will write tabel in cgram (address 40 of lcd
        setb RS
        clr RW
        setb EN
        clr EN
        inc dptr
        djnz r7,wr1
        ret
;*********************************************************************
;TABEL FOR 8 CHAR
;MADE SUCH THAT CHAR "G" IS SINKING DOWN
;*********************************************************************

tabel:
        .db 00001110b   ;char 1 of CGRAM
        .db 00010001b   ;1=high pixel
        .db 00010000b   ;0=low pix
        .db 00010000b
        .db 00010011b
        .db 00010001b
        .db 00010001b
        .db 00001110b

        .db 00000000b
        .db 00001110b   ;char 2 of CGRAM
        .db 00010001b   ;1=high pixel
        .db 00010000b   ;0=low pix
        .db 00010000b
        .db 00010011b
        .db 00010001b
        .db 00010001b

        .db 00000000b
        .db 00000000b
        .db 00001110b   ;char 3 of CGRAM
        .db 00010001b   ;1=high pixel
        .db 00010000b   ;0=low pix
        .db 00010000b
        .db 00010011b
        .db 00010001b


        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00001110b   ;char 4 of CGRAM
        .db 00010001b   ;1=high pixel
        .db 00010000b   ;0=low pix
        .db 00010000b
        .db 00010011b

        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00001110b   ;char 5 of CGRAM
        .db 00010001b   ;1=high pixel
        .db 00010000b   ;0=low pix
        .db 00010000b

        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00001110b   ;char 6 of CGRAM
        .db 00010001b   ;1=high pixel
        .db 00010000b   ;0=low pix

        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00001110b   ;char 7 of CGRAM
        .db 00010001b   ;1=high pixel

        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00000000b
        .db 00001110b   ;char 8 of CGRAM

        .end