86 lines
1.6 KiB
ArmAsm
86 lines
1.6 KiB
ArmAsm
PORTB = $6000
|
|
PORTA = $6001
|
|
DDRB = $6002
|
|
DDRA = $6003
|
|
|
|
E = %10000000
|
|
RW = %01000000
|
|
RS = %00100000
|
|
|
|
.org $8000
|
|
|
|
reset:
|
|
lda #%11111111 ; set all pins on port B to output
|
|
sta DDRB
|
|
lda #%11100000 ; set top 3 pins on port A to output
|
|
sta DDRA
|
|
|
|
lda #%00111000 ; set 8-bit mode, 2 line display, 5x8 font.
|
|
jsr command_to_lcd
|
|
lda #%00001110 ; set display and curson on, do not blink
|
|
jsr command_to_lcd
|
|
lda #%00000110 ; set entry mode increment and display shift off
|
|
jsr command_to_lcd
|
|
lda #%00000001
|
|
jsr command_to_lcd
|
|
|
|
ldx #0
|
|
print:
|
|
lda message,x
|
|
beq loop ; load sets zero flag (checked by beq) when it loads a zero byte.
|
|
jsr ASCII_to_lcd
|
|
inx
|
|
jmp print
|
|
|
|
loop:
|
|
jmp loop
|
|
|
|
; asciiz appends a 0 byte to the string
|
|
message: .asciiz "Hello, world! :D"
|
|
|
|
lcd_wait:
|
|
pha ; save porta to stack
|
|
lda #%00000000 ; set PORTB to input
|
|
sta DDRB
|
|
lcdbusy:
|
|
lda #RW
|
|
sta PORTA
|
|
lda #(RW | E)
|
|
sta PORTA
|
|
lda PORTB
|
|
and #%10000000 ; check LCD busy flag
|
|
bne lcdbusy ; branch if it is NOT set
|
|
|
|
lda #RW
|
|
sta PORTA
|
|
lda #%11111111 ; set PORTB to output again
|
|
sta DDRB
|
|
pla ; load stack value back to porta
|
|
rts ; RETURN
|
|
|
|
command_to_lcd:
|
|
jsr lcd_wait ; ensure LCD is not busy before sending instruction
|
|
sta PORTB
|
|
lda #0 ; clear RS/RW/E bits
|
|
sta PORTA
|
|
lda #E ; set enable bit to send instruction
|
|
sta PORTA
|
|
lda #0 ; clear RS/RW/E bits
|
|
sta PORTA
|
|
rts ; RETURN
|
|
|
|
ASCII_to_lcd:
|
|
jsr lcd_wait ; ensure LCD is not busy before sending instruction
|
|
sta PORTB
|
|
lda #RS ; RS set
|
|
sta PORTA
|
|
lda #(RS | E) ; RS and E set
|
|
sta PORTA
|
|
lda #RS ; RS set
|
|
sta PORTA
|
|
rts ; RETURN
|
|
|
|
.org $fffc
|
|
.word reset
|
|
.word $0000
|