mockingboard: interrupt playing works now

mockingboard/interrupt_test.s

@@ -95,13 +95,15 @@ forever_loop:
 	;=============================
 	; simple interrupt handler
 	;=============================
-interrupt_handler:
-	lda	$45	; the Apple II firmware messes with A when
-			; detecting BRK, so the value in $45 is the real one?
-			; also DISK II support uses this so you should disable
-			; interrupts if messing with the disk?
+	; On Apple II/6502 the interrupt handler jumps to address in 0xfffe
+	; This is in the ROM, which saves the registers
+	;   on older IIe it saved A to $45 (which could mess with DISK II)
+	;   newer IIe doesn't do that.
+	; It then calculates if it is a BRK or not (which trashes A)
+	; Then it sets up the stack like an interrupt and calls 0x3fe
 
-	pha		; save A (hardware saved Pflags for us)
+interrupt_handler:
+	pha		; save A
 
 	bit		$C404	; can clear interrupt by reading T1C-L
 

mockingboard/ksp_theme_interrupt.s

@@ -14,6 +14,11 @@
 	sta	DRAW_PAGE
 	sta	CH
 	sta	CV
+	sta	DONE_PLAYING
+
+	lda	#1
+	sta	MB_FRAME_DIFF
+
 	lda	#<mocking_message
 	sta	OUTL
 	lda	#>mocking_message
@@ -61,21 +66,108 @@ mockingboard_found:
 	lda	#>ksptheme
 	sta	INH
 
-new_frame:
-	ldy	#0
 	lda	(INL),Y		; read in frame delay
-	cmp	#$ff		; see if end
-	beq	done_play	; if so, done
+	sta	MB_FRAME_DIFF
+	inc	INL		; FIXME: should check if we oflowed
 
-	tax
-old_frame:
-	dex			; decrement the frame diff
-	beq	bottom_regs	; if not there yet, delay
-	jsr	delay_50Hz
-	jmp	old_frame
+	;=========================
+	; Setup Interrupt Handler
+	;=========================
+	; Vector address goes to 0x3fe/0x3ff
+	; FIXME: should chain any existing handler
 
+	lda	#<interrupt_handler
+	sta	$03fe
+	lda	#>interrupt_handler
+	sta	$03ff
+
+	;============================
+	; Enable 50Hz clock on 6522
+	;============================
+
+	lda	#$40		; Generate continuous interrupts, don't touch PB7
+	sta	$C40B		; ACR register
+	lda	#$7F		; clear all interrupt flags
+	sta	$C40E		; IER register (interrupt enable)
+
+	lda	#$C0
+	sta	$C40D		; IFR: 1100, enable interrupt on timer one oflow
+	sta	$C40E		; IER: 1100, enable timer one interrupt
+
+	lda	#$E7
+	sta	$C404		; write into low-order latch
+	lda	#$4f
+	sta	$C405		; write into high-order latch,
+				; load both values into counter
+				; clear interrupt and start counting
+
+	; 4fe7 / 1e6 = .020s, 50Hz
+
+	;============================
+	; Enable 6502 interrupts
+	;============================
+	;
+	cli		; clear interrupt mask
+
+
+	;============================
+	; Loop forever
+	;============================
+playing_loop:
+	lda	DONE_PLAYING
+	beq	playing_loop
+
+done_play:
+
+				; FIXME: disable timer on 6522
+				; FIXME: unhook interrupt handler
+
+	sei			; disable interrupts
+
+	jsr	clear_ay_left
+	jsr	clear_ay_right
+
+	lda	#0
+	sta	CH
+	lda	#3
+	sta	CV
+	lda	#<done_message
+	sta	OUTL
+	lda	#>done_message
+	sta	OUTH
+	jsr	move_and_print
+
+forever_loop:
+	jmp	forever_loop
+
+	;=============================
+	;=============================
+	; simple interrupt handler
+	;=============================
+	;=============================
+	; On Apple II/6502 the interrupt handler jumps to address in 0xfffe
+	; This is in the ROM, which saves the registers
+	;   on older IIe it saved A to $45 (which could mess with DISK II)
+	;   newer IIe doesn't do that.
+	; It then calculates if it is a BRK or not (which trashes A)
+	; Then it sets up the stack like an interrupt and calls 0x3fe
+
+interrupt_handler:
+	pha			; save A
+				; Should we save X and Y too?
+
+	bit	$C404		; can clear 6522 interrupt by reading T1C-L
+
+	inc	$0401		; DEBUG: increment text char
+
+	dec	MB_FRAME_DIFF
+	bne	done_interrupt
+
+
+
+
+	ldy	#0
 bottom_regs:
-	iny
 	lda	(INL),Y			; load low reg bitmask
 	sta	MASK
 	ldx	#$ff			; init to -1
@@ -139,6 +231,16 @@ top_regs_loop:
 	jmp	top_regs_loop
 
 done_with_masks:
+new_frame_diff:
+	iny
+	lda	(INL),Y		; read in frame delay
+	cmp	#$ff		; see if end
+	bne	not_done	; if so, done
+	inc	DONE_PLAYING	; set done playing flag
+	jmp	done_interrupt
+not_done:
+	sta	MB_FRAME_DIFF
+
 	iny
 	clc
 	tya
@@ -148,40 +250,12 @@ done_with_masks:
 	adc	INH
 	sta	INH
 
-	jsr	delay_50Hz
-
-	jmp	new_frame
-
-done_play:
-
-	jsr	clear_ay_left
-	jsr	clear_ay_right
-
-	lda	#0
-	sta	CH
-	lda	#3
-	sta	CV
-	lda	#<done_message
-	sta	OUTL
-	lda	#>done_message
-	sta	OUTH
-	jsr	move_and_print
-
-
-forever_loop:
-	jmp	forever_loop
+done_interrupt:
+	pla
+	rti
 
 
 
-delay_50Hz:
-
-	lda	#86
-	jsr	WAIT			; delay 1/2(26+27A+5A^2) us
-					; 50Hz = 20ms = 20000us
-					; 40000 = 26+27A+5A^2
-					; 5a^2+27a-39974 = 0
-					; A = 86.75
-	rts
 
 
 ;=========
@@ -199,7 +273,7 @@ delay_50Hz:
 ;=========
 ; strings
 ;=========
-mocking_message:	.asciiz "ASSUMING MOCKINGBOARD IN SLOT #4"
+mocking_message:	.asciiz "LOOKING FOR MOCKINGBOARD IN SLOT #4"
 not_message:		.byte   "NOT "
 found_message:		.asciiz "FOUND"
 done_message:		.asciiz "DONE PLAYING"

mockingboard/zp.inc

@@ -102,6 +102,8 @@ RANDOM_POINTER	EQU	$8F
 FRAME_COUNT	EQU	$90
 MB_ADDRL	EQU	$91
 MB_ADDRH	EQU	$92
+DONE_PLAYING	EQU	$93
+MB_FRAME_DIFF	EQU	$94
 
 SHIPY           EQU     $E4