; Phil Cranmer
; 16 July 2019

; 1602 LCD
; RS - Register select : 0 = Instruction, 1 = Data ( PA3 )
; Data - D4, D5, D6 & D7 : 4 bit data ( PA4, PA5, PA6 & PA7 )

; to set up 2 line 4-bit : 0x00 | 0x08 | 0x00
; LED1|LED2|Enable|RS|D4|D5|D6|D7


INIT:       jp START
            push af
            pop af

DLY:        ld b,10
DLP:        nop
            djnz DLP
            ret

DLYBG:      ld B,100 ; Load in 10
BLP:        nop
            djnz BLP
            ret

LCMD:       ; send command in a
            push af ; save a copy
            push af ; and another
            and 0xF0 ; remove lower nibble and send it
            out (0x01),a
            xor %00000101
            out (0x01),a
            xor %00000101
            out (0x01),a
            pop af ; fetch original value back
            sla a ; scoot it over 4 places
            sla a
            sla a
            sla a
            and 0xF0 ; remove lower nibble and send it
            out (0x01),a
            xor %00000101
            out (0x01),a
            xor %00000101
            out (0x01),a
            pop af ; fetch back initial value before returning
            nop
            nop
            nop
            nop
            nop
            ret

LDAT:       ; send data in a
            push af ; save a copy
            push af ; and another
            and 0xF0 ; remove lower nibble and send it
            xor %00001000 ; set LCD to data mode (RS)
            out (0x01),a
            xor %00000101
            out (0x01),a
            xor %00000101
            out (0x01),a
            pop af ; fetch original value back
            sla a ; scoot it over 4 places
            sla a
            sla a
            sla a
            and 0xF0 ; remove lower nibble and send it
            out (0x01),a
            xor %00001101
            out (0x01),a
            xor %00001101
            out (0x01),a
            pop af ; fetch back initial value before returning
            nop
            nop
            nop
            nop
            nop
            ret

START:      ld a,0xFF ; Load 255 into acc
            out (0x02),a ; Port B all outputs
            out (0x03),a ; Port A all outputs
BLNK:       ld a,0x01 ; Load 1 into acc
            out (0x01),a ; Turn on 1 output on port A
            call DLY
            ld a,0x00 ; Load 0 into acc
            out (0x01),a ; Turn off all output on port A
            call DLY
            ; setup 4-bit mode
            ld a,0x02
            call LCMD
            call LCMD
            call LCMD
            call LCMD
            ;ld a,%00100000
            ;call LCMD
            ;0x08 | 0x02  - send lines, font etc.
            ld a,0x28
            call LCMD
            ; 0x04 | 0x02 | 0x0 - Display on, cursor off, blink off
            ld a,0x0E
            call LCMD
            ;; 0x00 | 0x02 | 0x04 - default text direction
            ;ld a,%01100000
            ; Clear
            ld a,0x01
            call LCMD
            ; Move cursor to start
            ld a,0x80
            call LCMD
            ; Send some text
            ld a,'H'
            call LDAT
            ld a,'e'
            call LDAT
            ld a,'l'
            call LDAT
            ld a,'l'
            call LDAT
            ld a,'o'
            call LDAT
LOOP:       nop
            jp LOOP





; Call - go to sub routine
; RET - return
; DJNZ - Dec, jump not zero
; 10 = Dec, 0xA = Hex & %1010 = binary