; LCD Display Driver Demo.
; Timing code assumes 1.2MHz Clock
;LCD Registers addresses
LCD_CMD_WR equ 0
LCD_DATA_WR equ 1
LCD_BUSY_RD equ 2
LCD_DATA_RD equ 3
;LCD Commands
LCD_CLS equ 1
LCD_HOME equ 2
LCD_SETMODE equ 4
LCD_SETVISIBLE equ LCD_SHIFT equ 16
8
LCD_SETFUNCTION equ 32
LCD_SETCGADDR equ
LCD_SETDDADDR equ 128
;Reset vector
org 0000h
jmp start
;Start of the program
org 0100h
string1a:db ' !! A M A Z I N G !! '
db 0
string1b:db '!! A M A Z I N G !! '
db 0
string2:db ' A virtual LM032L... '
db 0
string3:db ' driven by a virtual '
db 0
string4:db ' 8051 processor!'
db 0
start: mov A,#038h
call wrcmd
loop: mov A,#LCD_SETVISIBLE+6 call wrcmd
mov R7,#2
loop2:
mov DPTR,#string1a
call wrstr
;Make the display & blink visible:
mov DPTR,#200
call wtms
mov A,#LCD_CLS call wrcmd
mov DPTR,#string1b
call wrstr
mov DPTR,#200
call wtms
mov A,#LCD_CLS call wrcmd
djnz R7,loop2
mov DPTR,#string1a
call wrstr
;Clear screen
;Clear screen
mov DPTR,#400
call wtms
mov A,#LCD_SETDDADDR+
call wrcmd
mov DPTR,#string2
call wrslow
mov DPTR,#200
call wtms
mov A,#LCD_CLS ;Clear screen
call wrcmd
mov DPTR,#string3
call wrslow
mov A,#LCD_SETDDADDR+
call wrcmd
mov DPTR,#string4
call wrslow
mov A,#LCD_SETVISIBLE+7 ;Show the blink cursor as well.
call wrcmd
mov DPTR,#2000
call wtms
mov A,#LCD_CLS ;Clear screen
call wrcmd
jmp loop
;Sub routine to write null terminated string at DPTR in program ram.
wrstr: mov R0,#LCD_DATA_WR
wrstr1: clr A
movc A,@A+DPTR
jz wrstr2
movx @R0,A
call wtbusy
inc DPTR
push DPL
push DPH
pop DPH
pop DPL
jmp wrstr1
wrstr2: ret
;Sub routine to write null terminated string at DPTR in program ram. Slowly
wrslow: mov R0,#LCD_DATA_WR
wrslw1: clr A
movc A,@A+DPTR
jz wrslw2
movx @R0,A
call wtbusy
inc DPTR
push DPL
push DPH
mov DPTR,#100
call wtms
pop DPH
pop DPL
jmp wrslw1
wrslw2: ret
;Sub routine to write command:
wrcmd: mov R0,#LCD_CMD_WR
movx @R0,A
jmp wtbusy
;Sub routine to write character:
wrchar: mov R0,#LCD_DATA_WR
movx @R0,A
;Subroutine to wait for busy clear
wtbusy: mov R1,#LCD_BUSY_RD
movx A,@r1
jb ACC.7,wtbusy
ret
;Wait for number of seconds in A
wtsec: push ACC
call wtms
pop ACC
dec A
jnz wtsec
ret
;Wait for number of milliseconds in DPTR
wtms: xrl DPL,#0FFh forming 2's complement
;Can't do DEC DPTR, so do the loop by
xrl DPH,#0FFh ;and incrementing instead.
inc DPTR
wtms1: mov TL0,#09Ch Clock
;100 ticks before overflow = 1ms at 1.2MHz
mov TH0,#0FFh
mov TMOD,#1 ;Timer 0 mode 1
setb TCON.4 ;Timer 0 runs
wtms2: jnb TCON.5,wtms2
clr TCON.4 ;Timer 0 stops
clr TCON.5
inc DPTR
mov A,DPL
orl A,DPH
jnz wtms1
ret
END
