; =============================================================================
; APPLIX 1616 NO-RAM STRING PRINTER ("Hi Keith")
; Fetches 8-byte font graphics from 0x00516144 and draws to VRAM at 0x00078000
; =============================================================================

.text
.org 0x500000			; Absolute Boot Start of ROM

; --- Hardware Vectors ---
.long 0x00000300		; Dummy Stack Pointer
.long BOOT_VECTOR		; Reset Vector

BOOT_VECTOR:
	JMP	START_DIAG(PC)	; Skip existing code block

; =============================================================================
; DIAGNOSTIC CODE ENTRY POINT
; =============================================================================
.org 0x51DB80
START_DIAG:
	MOVE.W	#0x2700,SR	; Disable interrupts

; -----------------------------------------------------------------------------
; 1. CONFIGURE VIDLATCH & CLEAR VIDEO RAM
; -----------------------------------------------------------------------------
	MOVEA.L	#0x600101,A0	; A0 = VIDLATCH
	MOVE.B	#0x0F,(A0)	; Point video hardware to 0x00078000 bank

	MOVEA.L	#0x00078000,A1	; Start of Video RAM
	MOVEA.L	#0x00080000,A2	; End of Video RAM boundary
	MOVE.W	#0x0000,D0	; Clear value (Black pixels)

CLEAR_VRAM:
	MOVE.W	D0,(A1)+
	CMPA.L	A2,A1
	BNE.S	CLEAR_VRAM

; -----------------------------------------------------------------------------
; 2. INITIALIZE MC6845 CRTC FOR PAL VIDEO
; -----------------------------------------------------------------------------
	MOVEA.L	#0x700180,A3	; A3 = CRTCADDR
	MOVEA.L	#0x700182,A4	; A4 = CRTCDATA

	MOVE.B	#0,(A3)	;
	MOVE.B	#0x3F,(A4)	; R0: Horizontal Total
	MOVE.B	#1,(A3)	;
	MOVE.B	#0x28,(A4)	; R1: Horizontal Displayed
	MOVE.B	#2,(A3)	;
	MOVE.B	#0x2D,(A4)	; R2: Horizontal Sync Position
	MOVE.B	#3,(A3)	;
	MOVE.B	#0x0A,(A4)	; R3: Sync Widths
	MOVE.B	#4,(A3)	;
	MOVE.B	#0x26,(A4)	; R4: Vertical Total
	MOVE.B	#5,(A3)	;
	MOVE.B	#0x00,(A4)	; R5: Vertical Total Adjust
	MOVE.B	#6,(A3)	;
	MOVE.B	#0x19,(A4)	; R6: Vertical Displayed
	MOVE.B	#7,(A3)	;
	MOVE.B	#0x22,(A4)	; R7: Vertical Sync Position
	MOVE.B	#8,(A3)	;
	MOVE.B	#0x00,(A4)	; R8: Interlace Mode
	MOVE.B	#9,(A3)	;
	MOVE.B	#0x07,(A4)	; R9: Max Scan Line Address
	MOVE.B	#10,(A3)	;
	MOVE.B	#0x20,(A4)	; R10: Cursor Start Line
	MOVE.B	#11,(A3)	;
	MOVE.B	#0x00,(A4)	; R11: Cursor End Line
	MOVE.B	#12,(A3)	;
	MOVE.B	#0x00,(A4)	; R12: Start Address High
	MOVE.B	#13,(A3)	;
	MOVE.B	#0x00,(A4)	; R13: Start Address Low

; -----------------------------------------------------------------------------
; 3. RENDER "Hi Keith" TO SCREEN (NO STACK, NO RAM UTILITY)
; -----------------------------------------------------------------------------
	; Set up base pointers
	MOVEA.L	#0x00516144,A1	; A1 = Font Table base address
	MOVEA.L	#0x00078000,A2	; A2 = Current destination pixel column
	MOVE.L	#4096,D2	; D2 = 4096 byte stride for interlaced lines

	; --- PRINT 'H' (ASCII 72) ---
	; Offset = 72 * 8 = 576 bytes
	LEA	576(A1),A5	; A5 points to font data for 'H'
	MOVEA.L	A2,A6		; A6 copies current screen base column pointer
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2;
	MOVE to the next horizontal screen byte column

	; --- PRINT 'i' (ASCII 105) ---
	; Offset = 105 * 8 = 840 bytes
	LEA	840(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2

	; --- PRINT ' ' (ASCII 32) ---
	; Offset = 32 * 8 = 256 bytes
	LEA	256(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2

	; --- PRINT 'K' (ASCII 75) ---
	; Offset = 75 * 8 = 600 bytes
	LEA	600(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2

	; --- PRINT 'e' (ASCII 101) ---
	; Offset = 101 * 8 = 808 bytes
	LEA	808(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2

	; --- PRINT 'i' (ASCII 105) ---
	; Offset = 105 * 8 = 840 bytes
	LEA	840(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2

	; --- PRINT 't' (ASCII 116) ---
	; Offset = 116 * 8 = 928 bytes
	LEA	928(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)
	ADDQ.L	#1,A2

	; --- PRINT 'h' (ASCII 104) ---
	; Offset = 104 * 8 = 832 bytes
	LEA	832(A1),A5
	MOVEA.L	A2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)	;
	ADDA.L	D2,A6
	MOVE.B	(A5)+,(A6)

; -----------------------------------------------------------------------------
; 4. INITIALIZE ZILOG SCC & INF-LOOP (Keeps Serial Active as Backup)
; -----------------------------------------------------------------------------
	MOVEA.L	#0x700004,A5		; A5 = SCCAC
	MOVE.B	#9,(A5)	;
	MOVE.B	#0x40,(A5)
	MOVE.B	#4,(A5)	;
	MOVE.B	#0x44,(A5)
	MOVE.B	#3,(A5)	;
	MOVE.B	#0xC0,(A5)
	MOVE.B	#5,(A5)	;
	MOVE.B	#0x60,(A5)
	MOVE.B	#11,(A5)	;
	MOVE.B	#0x50,(A5)
	MOVE.B	#12,(A5)	;
	MOVE.B	#0x0A,(A5)
	MOVE.B	#13,(A5)	;
	MOVE.B	#0x00,(A5)
	MOVE.B	#14,(A5)	;
	MOVE.B	#0x01,(A5)
	MOVE.B	#3,(A5)	;
	MOVE.B	#0xC1,(A5)
	MOVE.B	#5,(A5)	;
	MOVE.B	#0x6A,(A5)

DIAG_LOOP:
	MOVE.B	#0,(A5)		; want reg 0
	MOVE.B	(A5),D0		; read reg
	AND.B 	#0x04,D0	; check ready to send
	BEQ.S	DIAG_LOOP

	MOVEA.L	#0x700006,A6
	MOVE.B	#0x41,(A6)		; Blast 'A' out to serial terminal
	BRA.S	DIAG_LOOP