From 20d9b2ed10986e10d86357b459586e122b5a06b2 Mon Sep 17 00:00:00 2001
From: Ivan Izaguirre <ivanizag@gmail.com>
Date: Tue, 12 Nov 2019 23:47:48 +0100
Subject: [PATCH] Partial FASTChip emulation.

---
 README.md       |  1 +
 apple2Setup.go  |  7 +++++
 apple2main.go   | 17 ++++++++----
 cardFastChip.go | 72 +++++++++++++++++++++++++++++++++++++++++++++++++
 cardVidHD.go    |  2 +-
 5 files changed, 93 insertions(+), 6 deletions(-)
 create mode 100644 cardFastChip.go

diff --git a/README.md b/README.md
index d72b559..6bab768 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@ Portable emulator of an Apple II+ or //e. Written in Go.
     - Bootable hard disk card
     - Apple //e 80 columns with 64Kb extra RAM
     - VidHd, limited to the ROM signature and SHR as used by Total Replay
+    - FASTChip, limited to what Total Replay needs to set and clear fast mode
 - Graphic modes:
     - Text 40 columns
     - text 80 columns (Apple //e only)
diff --git a/apple2Setup.go b/apple2Setup.go
index 0aa0072..735b31e 100644
--- a/apple2Setup.go
+++ b/apple2Setup.go
@@ -137,6 +137,13 @@ func (a *Apple2) AddVidHD(slot int) {
 	a.insertCard(&c, slot)
 }
 
+// AddFastChip adds a card with the signature of VidHD
+func (a *Apple2) AddFastChip(slot int) {
+	var c cardFastChip
+	c.loadRom(buildFastChipRom())
+	a.insertCard(&c, slot)
+}
+
 // AddLanguageCard inserts a 16Kb card
 func (a *Apple2) AddLanguageCard(slot int) {
 	a.insertCard(&cardLanguage{}, slot)
diff --git a/apple2main.go b/apple2main.go
index 95a8b20..f504b2c 100644
--- a/apple2main.go
+++ b/apple2main.go
@@ -49,14 +49,18 @@ func MainApple() *Apple2 {
 		"saturnCardSlot",
 		-1,
 		"slot for the 256kb Saturn card. -1 for none")
-	thunderClockCardSlot := flag.Int(
-		"thunderClockCardSlot",
-		4,
-		"slot for the ThunderClock Plus card. -1 for none")
 	vidHDCardSlot := flag.Int(
 		"vidHDSlot",
 		2,
 		"slot for the VidHD card, -1 for none")
+	fastChipCardSlot := flag.Int(
+		"fastChipSlot",
+		3,
+		"slot for the FASTChip accelerator card, -1 for none")
+	thunderClockCardSlot := flag.Int(
+		"thunderClockCardSlot",
+		4,
+		"slot for the ThunderClock Plus card. -1 for none")
 	mono := flag.Bool(
 		"mono",
 		false,
@@ -185,9 +189,12 @@ func MainApple() *Apple2 {
 			panic(err)
 		}
 	}
-	if *vidHDCardSlot > 0 {
+	if *vidHDCardSlot >= 0 {
 		a.AddVidHD(*vidHDCardSlot)
 	}
+	if *fastChipCardSlot >= 0 {
+		a.AddFastChip(*fastChipCardSlot)
+	}
 	if *disk2Slot > 0 {
 		err := a.AddDisk2(*disk2Slot, *disk2RomFile, *diskImage)
 		if err != nil {
diff --git a/cardFastChip.go b/cardFastChip.go
new file mode 100644
index 0000000..23415b4
--- /dev/null
+++ b/cardFastChip.go
@@ -0,0 +1,72 @@
+package apple2
+
+/*
+Simulates just what is needed to make Total Replay use fast mode. Can change
+from controlled speed to max speed the emulator can do.
+Note: It ends up not being useful for Total Replay as loading from HD is already
+very fast. HD blocks are loaded directly on the emulated RAM.
+
+See:
+	https://github.com/a2-4am/4cade/blob/master/src/hw.accel.a
+	http://www.a2heaven.com/webshop/resources/pdf_document/18/82/c.pdf
+
+*/
+
+type cardFastChip struct {
+	cardBase
+	unlocked      bool
+	unlockCounter uint8
+	enabled       bool
+	accelerated   bool
+}
+
+func buildFastChipRom() []uint8 {
+	data := make([]uint8, 256)
+	return data
+}
+
+const (
+	fastChipUnlockToken   = 0x6a
+	fastChipUnlockRepeats = 4
+	fastChipNormalSpeed   = uint8(9)
+)
+
+func (c *cardFastChip) assign(a *Apple2, slot int) {
+	// The softswitches are outside the card reserved ss
+	// Only writes are implemented to avoid conflicts with the joysticks
+	a.io.addSoftSwitchW(0x6a, func(_ *ioC0Page, value uint8) {
+		if value == fastChipUnlockToken {
+			c.unlockCounter++
+			if c.unlockCounter >= fastChipUnlockRepeats {
+				c.unlocked = true
+			}
+		} else {
+			c.unlockCounter = 0
+			c.unlocked = false
+		}
+	}, "FASTCHIP-LOCK")
+
+	a.io.addSoftSwitchW(0x6b, func(_ *ioC0Page, _ uint8) {
+		if c.unlocked {
+			c.enabled = true
+		}
+	}, "FASTCHIP-ENABLE")
+
+	a.io.addSoftSwitchW(0x6d, func(_ *ioC0Page, value uint8) {
+		if c.unlocked && c.enabled {
+			newAccelerated := (value > fastChipNormalSpeed)
+			if newAccelerated == c.accelerated {
+				// No change requested
+				return
+			}
+			if newAccelerated {
+				a.requestFastMode()
+			} else {
+				a.releaseFastMode()
+			}
+			c.accelerated = newAccelerated
+		}
+	}, "FASTCHIP-SPEED")
+
+	c.cardBase.assign(a, slot)
+}
diff --git a/cardVidHD.go b/cardVidHD.go
index 7658003..f262fae 100644
--- a/cardVidHD.go
+++ b/cardVidHD.go
@@ -27,7 +27,7 @@ const (
 )
 
 func (c *cardVidHD) assign(a *Apple2, slot int) {
-	// The softswitches are outside the card reverded ss
+	// The softswitches are outside the card reserved ss
 	a.io.addSoftSwitchR(0x22, notImplementedSoftSwitchR, "VIDHD-TBCOLOR")
 	a.io.addSoftSwitchW(0x22, notImplementedSoftSwitchW, "VIDHD-TBCOLOR")
 	a.io.addSoftSwitchR(0x29, getStatusSoftSwitch(ioDataNewVideo), "VIDHD-NEWVIDEO")