From 7d5ccc8e0cbe766d329cf9f66308f997d9bef6e8 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sat, 21 Dec 2024 17:34:50 -0500
Subject: [PATCH] xmas24: test iic/ii+/gs support

---
 demos/xmas_2024/Makefile     |  2 +-
 demos/xmas_2024/hardware.inc | 13 +++++-
 demos/xmas_2024/start.s      |  2 +-
 demos/xmas_2024/vblank.s     | 78 +++++++++++++++++++++++++++++-------
 4 files changed, 77 insertions(+), 18 deletions(-)

diff --git a/demos/xmas_2024/Makefile b/demos/xmas_2024/Makefile
index 0b69aff1..e8c70616 100644
--- a/demos/xmas_2024/Makefile
+++ b/demos/xmas_2024/Makefile
@@ -42,7 +42,7 @@ qload.o:	zp.inc hardware.inc music.inc qload.s \
 	wait.s wait_a_bit.s \
 	lc_detect.s gr_fast_clear.s \
 	text_print.s start.s \
-	hgr_table.s gs_interrupt.s \
+	hgr_table.s gs_interrupt.s vblank.s \
 	zx02_optim.s wait_keypress.s hardware_detect.s \
 	pt3_lib_detect_model.s pt3_lib_mockingboard_detect.s \
 	pt3_lib_mockingboard_setup.s interrupt_handler.s \
diff --git a/demos/xmas_2024/hardware.inc b/demos/xmas_2024/hardware.inc
index 1cf29d20..1aba7a66 100644
--- a/demos/xmas_2024/hardware.inc
+++ b/demos/xmas_2024/hardware.inc
@@ -8,11 +8,14 @@ CLR80COL	=	$C000	; PAGE1/PAGE1 normal
 SET80COL	=	$C001	; PAGE1/PAGE2 switches PAGE1 in Aux instead
 EIGHTYCOLOFF	=	$C00C
 EIGHTYCOLON	=	$C00D
+
+RDVBLBAR	=	$C019	; iic
 TBCOLOR		=	$C022	; IIgs text fg/bg colors
 NEWVIDEO	=	$C029	; IIgs graphics modes
 SPEAKER		=	$C030
 CLOCKCTL	=	$C034	; bits 0-3 are IIgs border color
 CYAREG		=	$C036	; iigs motor detect and clock speed
+RDVBLMSK	=	$C041	; iic read vbl interrupt
 SET_GR		=	$C050
 SET_TEXT	=	$C051
 FULLGR		=	$C052
@@ -22,10 +25,18 @@ PAGE2		=	$C055
 LORES		=	$C056	; Enable LORES graphics
 HIRES		=	$C057	; Enable HIRES graphics
 AN3		=	$C05E	; Annunciator 3
+DISVBL		=	$C05B	; (write) (iic) (ioudison) disable VBL interrupt
+ENVBL		=	$C05B	; (write) (iic) (ioudison) enable VBL interrupt
+CLRAN3		=	$C05E	; (write) in 80-col mode, enable double graphics
+SETAN3		=	$C05F	; (write) in 80-col mode, disable double graphics
 
 PADDLE_BUTTON0	=	$C061
 PADDL0		=	$C064
-PTRIG		=	$C070
+PTRIG		=	$C070	; analog input reset / reset VBL interrupt (iic)
+
+IOUDISON	=	$C07E	; (write) disable IOU
+IOUDISOFF	=	$C07F	; (write) enable IOU
+
 
 ; APPLESOFT BASIC ROUTINES
 
diff --git a/demos/xmas_2024/start.s b/demos/xmas_2024/start.s
index 32f15080..2351ea2e 100644
--- a/demos/xmas_2024/start.s
+++ b/demos/xmas_2024/start.s
@@ -188,7 +188,7 @@ no_mockingboard_string:
 
 ;             0123456789012345678901234567890123456789
 title_string:
-.byte 0,4, "XMAS 2024",0
+.byte 0,4, "XMAS 2024 (V1.1)",0
 .byte 0,6, "BY THE GUINEA PIG GANG",0
 .byte 0,8, "CODE:  VINCE 'DEATER' WEAVER",0
 .byte 0,9, "ART:   GUINEAGIRL2424",0
diff --git a/demos/xmas_2024/vblank.s b/demos/xmas_2024/vblank.s
index c9839a7b..bcdcbab7 100644
--- a/demos/xmas_2024/vblank.s
+++ b/demos/xmas_2024/vblank.s
@@ -14,10 +14,19 @@ VBLANK	= $C019		;
 ; TODO: patch this to a RTS on non-IIe systems
 
 wait_vblank:
-;	Assume Apple IIe
-;	lda	APPLEII_MODEL
-;	cmp	#'e'
-;	bne	no_vblank
+
+	lda	APPLEII_MODEL
+
+	cmp	#'e'
+	beq	wait_vblank_iie
+
+	cmp	#'g'
+	beq	wait_vblank_iigs
+
+;	cmp	#'c'
+;	beq	wait_vblank_iic
+
+	bne	no_vblank
 
 ; 4cade does this, the opposite of the way were doing it originally
 
@@ -33,16 +42,55 @@ wait_vblank_done_iie:
 	lda	VBLANK
 	bmi	wait_vblank_done_iie	; repeat until positive (start vblank)
 					; in vblank
-no_vblank:
-
-.if 0
-wait_vblank_iie:
-	lda	VBLANK
-	bmi	wait_vblank_iie		; wait for positive (in vblank)
-wait_vblank_done_iie:
-	lda	VBLANK			; wait for negative (vlank done)
-	bpl	wait_vblank_done_iie
-no_vblank:
-.endif
 
 	rts
+
+wait_vblank_iigs:
+	lda	VBLANK
+	bpl	wait_vblank_iigs	; repeat until negative
+					; not in vblank
+wait_vblank_done_iigs:
+	lda	VBLANK
+	bmi	wait_vblank_done_iigs	; repeat until positive (start vblank)
+					; in vblank
+
+	rts
+
+
+; NOTE: we don't support this as we have to handle interrupts
+;	for music and we'd have to hack up the irq handler
+;	to differentiate VBLANK from others
+
+; alternate implementation by Oliver Schmidt
+; from https://github.com/cc65/cc65/blob/master/libsrc/apple2/waitvsync.s
+
+wait_vblank_iic:
+;	sei			; disables interrupts
+	sta	IOUDISOFF
+	lda	RDVBLMSK
+	bit	ENVBL
+	bit	PTRIG		; Reset VBL interrupt flag
+
+wviim:
+	bit	RDVBLBAR
+	bpl	wviim
+
+	asl
+	bcs	wviip		; VBL interrupts were already enabled
+	bit	DISVBL
+wviip:
+	sta	IOUDISON        ; IIc Tech Ref Man: The firmware normally leaves IOUDIS on.
+;       cli                     ; re-enable interrupts
+
+	rts
+
+
+no_vblank:
+	; pause a bit?
+
+	lda	#50
+	jsr	wait
+
+	rts
+
+