; PPI_Synced_LED-LCD_Test.asm


; Z80 v1.1 Double-Time Synced LED/LCD Test
; Port A ($08) = LCD Data
; Port B ($09) = LED Bar Graph
; Port C High ($0A) = LCD Control: PC5=RS, PC6=R/W, PC7=E

.ORG $0000
    DI
    ; 1. Initialize PPI (All Ports Output - $80)
    LD A, $80
    OUT ($0B), A

    ; 2. LCD Init Sequence
    CALL LONG_DELAY
    LD A, $38           ; 8-bit, 2-line mode
    CALL LCD_CMD		; Line 60.
    LD A, $0C           ; Display ON, No Cursor
    CALL LCD_CMD
    LD A, $01           ; Clear Display
    CALL LCD_CMD		
    CALL LONG_DELAY		; Line 81.

RESTART_ALL:
    LD HL, MESSAGE      ; Point to start of string
    LD C, 13            ; String length ("Z80 SYSTEM OK")
    LD B, $01           ; Initialize LED pattern (Bit 0)

SYNC_LOOP:
    ; --- Part A: Update LED Bar ---
    LD A, B
    OUT ($09), A        ; Update LED Bar (Port B)
    
    ; --- Part B: Print One Character ---
    LD A, (HL)          ; Get current character from HL
    CALL LCD_DATA       ; Print to LCD (Port A + Port C). line 66.
    
    ; --- Part C: Update Iterators ---
    INC HL              ; Move to next character
    
    ; Rotate LED pattern
    LD A, B
    RLC A               ; Rotate Accumulator Left
    LD B, A             ; Save new pattern for next loop

    ; --- Part D: Double-Time Delay ---
    CALL FAST_SYNC_DELAY ; Reduced delay for double speed
    
    DEC C               ; Decrement character count
    JR NZ, SYNC_LOOP    ; Loop until string is done

    ; 3. End of string: Clear and start over
    LD A, $01           ; Clear Display command
    CALL LCD_CMD
    CALL LONG_DELAY
    JP RESTART_ALL

; --- LCD Subroutines (Hardware Verified: PC5=RS, PC6=RW, PC7=E) ---
LCD_CMD:
    OUT ($08), A        ; Cmd to Port A
    LD A, $00           ; RS=0, RW=0, E=0
    OUT ($0A), A		; Port C.
    JR LCD_PULSE		; Line 71.

LCD_DATA:
    OUT ($08), A        ; Data to Port A
    LD A, $20           ; RS=1 (PC5 High), RW=0, E=0
    OUT ($0A), A

LCD_PULSE:
    OR $80              ; E=1 (PC7 High)
    OUT ($0A), A
    PUSH AF             ; Settle time for breadboard capacitance
    POP AF
    AND $7F             ; E=0 (PC7 Low)
    OUT ($0A), A
    RET

; --- Delays ---
LONG_DELAY:             ; Used for Init and Clear
    LD DE, $8000
    JR D_LOOP
    
FAST_SYNC_DELAY:        ; ~50ms delay for double-time speed
    LD DE, $4000
    
D_LOOP:
    DEC DE
    LD A, D
    OR E
    JR NZ, D_LOOP
    RET

MESSAGE: .DB "Z80 SYSTEM OK"

.END