From cccb0583db887b65182155c90cc7a81ef3d3b6b9 Mon Sep 17 00:00:00 2001
From: Ivan Izaguirre <ivanizag@gmail.com>
Date: Fri, 17 May 2019 09:54:49 +0200
Subject: [PATCH] Support for the Saturn 128KB card

---
 apple2/apple2.go     |   7 +++
 apple2/cardSaturn.go | 146 +++++++++++++++++++++++++++++++++++++++++++
 main.go              |   3 +-
 3 files changed, 155 insertions(+), 1 deletion(-)
 create mode 100644 apple2/cardSaturn.go

diff --git a/apple2/apple2.go b/apple2/apple2.go
index fb5ec15..62e6b15 100644
--- a/apple2/apple2.go
+++ b/apple2/apple2.go
@@ -77,6 +77,13 @@ func (a *Apple2) AddLanguageCard(slot int) {
 	d.applyState()
 }
 
+// AddSaturnCard inserts a 128Kb card
+func (a *Apple2) AddSaturnCard(slot int) {
+	d := newCardSaturn()
+	d.cardBase.insert(a, slot)
+	d.applyState()
+}
+
 // ConfigureStdConsole uses stdin and stdout to interface with the Apple2
 func (a *Apple2) ConfigureStdConsole(stdinKeyboard bool, stdoutScreen bool) {
 	if !stdinKeyboard && !stdoutScreen {
diff --git a/apple2/cardSaturn.go b/apple2/cardSaturn.go
new file mode 100644
index 0000000..3ed7e73
--- /dev/null
+++ b/apple2/cardSaturn.go
@@ -0,0 +1,146 @@
+package apple2
+
+/*
+
+RAM card with 128Kb. It's like 8 language cards.
+
+http://www.applelogic.org/files/SATURN128MAN.pdf
+
+*/
+
+type cardSaturn struct {
+	cardBase
+	readState   bool
+	writeState  int
+	activeBank  int
+	activeBlock int
+	ramBankA    [8]*memoryRange // First 4kb to map in 0xD000-0xDFFF
+	ramBankB    [8]*memoryRange // Second 4kb to map in 0xD000-0xDFFF
+	ramUpper    [8]*memoryRange // Upper 8kb to map in 0xE000-0xFFFF
+}
+
+const (
+	// Write enabling requires two sofstwitch accesses
+	saturnWriteDisabled    = 0
+	saturnWriteHalfEnabled = 1
+	saturnWriteEnabled     = 2
+)
+
+func newCardSaturn() *cardSaturn {
+	var c cardSaturn
+	c.readState = false
+	c.writeState = lcWriteEnabled
+	c.activeBank = 1
+
+	for i := 0; i < 8; i++ {
+		c.ramBankA[i] = newMemoryRange(0xd000, make([]uint8, 0x1000))
+		c.ramBankB[i] = newMemoryRange(0xd000, make([]uint8, 0x1000))
+		c.ramUpper[i] = newMemoryRange(0xe000, make([]uint8, 0x2000))
+	}
+	for i := 0x0; i <= 0xf; i++ {
+		iCopy := i
+		c.ssr[i] = func(*ioC0Page) uint8 {
+			c.ssAction(iCopy)
+			return 0
+		}
+		c.ssw[i] = func(*ioC0Page, uint8) {
+			// Writing resets write count (from A2AUDIT)
+			c.writeState = lcWriteDisabled
+		}
+	}
+	return &c
+}
+
+func (c *cardSaturn) ssAction(ss int) {
+	switch ss {
+	case 0:
+		// RAM read, no writes
+		c.activeBank = 0
+		c.readState = true
+		c.writeState = lcWriteDisabled
+	case 1:
+		// ROM read, RAM write
+		c.activeBank = 0
+		c.readState = false
+		c.writeState++
+	case 2:
+		// ROM read, no writes
+		c.activeBank = 0
+		c.readState = false
+		c.writeState = lcWriteDisabled
+	case 3:
+		//RAM read, RAM write
+		c.activeBank = 0
+		c.readState = true
+		c.writeState++
+	case 4:
+		c.activeBlock = 0
+	case 5:
+		c.activeBlock = 1
+	case 6:
+		c.activeBlock = 2
+	case 7:
+		c.activeBlock = 3
+	case 8:
+		// RAM read, no writes
+		c.activeBank = 1
+		c.readState = true
+		c.writeState = lcWriteDisabled
+	case 9:
+		// ROM read, RAM write
+		c.activeBank = 1
+		c.readState = false
+		c.writeState++
+	case 10:
+		// ROM read, no writes
+		c.activeBank = 1
+		c.readState = false
+		c.writeState = lcWriteDisabled
+	case 11:
+		//RAM read, RAM write
+		c.activeBank = 1
+		c.readState = true
+		c.writeState++
+	case 12:
+		c.activeBlock = 0
+	case 13:
+		c.activeBlock = 1
+	case 14:
+		c.activeBlock = 2
+	case 15:
+		c.activeBlock = 3
+	}
+
+	if c.writeState > lcWriteEnabled {
+		c.writeState = lcWriteEnabled
+	}
+
+	c.applyState()
+}
+
+func (c *cardSaturn) getActiveBank() [8]*memoryRange {
+	if c.activeBank == 0 {
+		return c.ramBankA
+	}
+	return c.ramBankB
+}
+
+func (c *cardSaturn) applyState() {
+	mmu := c.a.mmu
+	block := c.activeBlock
+
+	if c.readState {
+		mmu.setPagesRead(0xd0, 0xdf, c.getActiveBank()[block])
+		mmu.setPagesRead(0xe0, 0xff, c.ramUpper[block])
+	} else {
+		mmu.setPagesRead(0xd0, 0xff, mmu.physicalROM)
+	}
+
+	if c.writeState == lcWriteEnabled {
+		mmu.setPagesWrite(0xd0, 0xdf, c.getActiveBank()[block])
+		mmu.setPagesWrite(0xe0, 0xff, c.ramUpper[block])
+	} else {
+		mmu.setPagesWrite(0xd0, 0xff, nil)
+	}
+
+}
diff --git a/main.go b/main.go
index a03d1aa..dd4ebe6 100644
--- a/main.go
+++ b/main.go
@@ -69,7 +69,8 @@ func main() {
 
 	log := false
 	a := apple2.NewApple2(*romFile, *charRomFile, *cpuClock, !*mono, *fastDisk, *panicSS)
-	a.AddLanguageCard(0)
+	//a.AddLanguageCard(0)
+	a.AddSaturnCard(0)
 	if *disk2Slot > 0 {
 		a.AddDisk2(*disk2Slot, *disk2RomFile, *diskImage)
 	}