jp main     ; Startup vector: DO NOT MOVE! Must be the first instruction

; Tests TM404A, on ports 2 and 3

IO_2: EQU 0x40
IO_3: EQU 0x60

LCD_TOP_INSTR_REG: EQU IO_2
LCD_TOP_DATA_REG: EQU IO_2 + 1
LCD_BOTTOM_INSTR_REG: EQU IO_3
LCD_BOTTOM_DATA_REG: EQU IO_3 + 1


; Inits the lcd display
LCD4004_init:
    ; --- Init first controller ---

    ; The following are documented as in the datasheet: RS R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
    ; Function set: 0 0 0 0 1 DL N F 0 0 (DL: 8-bit/4-bit, N: number of display lines 2/1, F: Font type 11dots/8dots)
    ; 0000111000 (8 bit, 2 lines)
    ld a,0x38
    out (LCD_TOP_INSTR_REG),a

    call LCD4004_wait_busy_clear

    ; Display ON/OFF Control: 0 0 0 0 0 0 1 D C B (D: display on/off, C: cursor on/off, B: blinking cursor on/off)
    ; 0000001111 (display on, blinking cursor)
    ld a,0x0F
    out (LCD_TOP_INSTR_REG),a

    call LCD4004_wait_busy_clear

    ; Clear display
    ; 0000000001
    ld a,0x01
    out (LCD_TOP_INSTR_REG),a

    call LCD4004_wait_busy_clear

    ; --- Init second controller ---

    ; The following are documented as in the datasheet: RS R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
    ; Function set: 0 0 0 0 1 DL N F 0 0 (DL: 8-bit/4-bit, N: number of display lines 2/1, F: Font type 11dots/8dots)
    ; 0000111000 (8 bit, 2 lines)
    ld a,0x38
    out (LCD_BOTTOM_INSTR_REG),a

    call LCD4004_wait_busy_clear

    ; Display ON/OFF Control: 0 0 0 0 0 0 1 D C B (D: display on/off, C: cursor on/off, B: blinking cursor on/off)
    ; 0000001111 (display on, blinking cursor)
    ld a,0x0F
    out (LCD_BOTTOM_INSTR_REG),a

    call LCD4004_wait_busy_clear

    ; Clear display
    ; 0000000001
    ld a,0x01
    out (LCD_BOTTOM_INSTR_REG),a

    call LCD4004_wait_busy_clear

    ret


; Prints string
; @param BC Pointer to a null-terminated string first character
LCD4004_TOP_print:
    ld a, (bc)  ; bc is the pointer to passed string's first char
    cp 0        ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
    ret z       ; if prev compare is true (Z flag set), string is finished, return
    out (LCD_TOP_DATA_REG),a    ; output char
    call LCD4004_wait_busy_clear     ; wait for the lcd to execute (busy signal check)
    inc bc ; increment bc to move to next char
    jp LCD4004_TOP_print

; Prints string
; @param BC Pointer to a null-terminated string first character
LCD4004_BOTTOM_print:
    ld a, (bc)  ; bc is the pointer to passed string's first char
    cp 0        ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
    ret z       ; if prev compare is true (Z flag set), string is finished, return
    out (LCD_BOTTOM_DATA_REG),a    ; output char
    call LCD4004_wait_busy_clear     ; wait for the lcd to execute (busy signal check)
    inc bc ; increment bc to move to next char
    jp LCD4004_BOTTOM_print

; Waits for the busy flag to be clear, indicating the LCD controllers to have finished their work
LCD4004_wait_busy_clear:
    ret
    in a, (LCD_TOP_INSTR_REG)    ; reads the status
    rla ; busy flag is DB7, so we shift it into carry to check it
    jp c, LCD4004_wait_busy_clear ; if carry is set, lcd is busy
    in a, (LCD_BOTTOM_INSTR_REG)    ; reads the status
    rla ; busy flag is DB7, so we shift it into carry to check it
    jp c, LCD4004_wait_busy_clear ; if carry is set, lcd is busy
    ret

; --- TEST CODE ---
main:
    TEST_STR_80: DB "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam augue tortor sed.",0  ; null terminated string
    TEST_STR_85: DB "2Lorem ipsum dolor sit amet, consectetur adipiscing elit praesent pellentesque nisi.",0  ; null terminated string

    ; Init display
    call LCD4004_init

    ; Write string on first 2 lines
    ld bc, TEST_STR_80
    call LCD4004_TOP_print

    ; Write long string on last 2 lines (to see how it wraps)
    ld bc, TEST_STR_85
    call LCD4004_BOTTOM_print

    halt