Split IO into its own module

mmu/io.go

@@ -0,0 +1,176 @@
+package mmu
+
+import (
+	"fmt"
+	"mos6502go/keyboard"
+)
+
+// https://mirrors.apple2.org.za/apple.cabi.net/Languages.Programming/MemoryMap.IIe.64K.128K.txt
+
+const (
+	KEYBOARD = 0xC000 // keyboard data (latched) (RD-only)
+	CLR80COL = 0xC000 // use 80-column memory mapping (WR-only)
+	SET80COL = 0xC001
+	CLRAUXRD = 0xC002 // read from auxilliary 48K
+	SETAUXRD = 0xC003
+	CLRAUXWR = 0xC004 // write to auxilliary 48K
+	SETAUXWR = 0xC005
+	CLRCXROM = 0xC006 // use external slot ROM
+	SETCXROM = 0xC007
+	CLRAUXZP = 0xC008 // use auxilliary ZP, stack, & LC
+	SETAUXZP = 0xC009
+	CLRC3ROM = 0xC00A // use external slot C3 ROM
+	SETC3ROM = 0xC00B
+	CLR80VID = 0xC00C // use 80-column display mode
+	SET80VID = 0xC00D
+	CLRALTCH = 0xC00E // use alternate character set ROM
+	SETALTCH = 0xC00F
+	STROBE   = 0xC010 // strobe (unlatch) keyboard data
+
+	RDLCBNK2 = 0xC011 // reading from LC bank $Dx 2
+	RDLCRAM  = 0xC012 // reading from LC RAM
+	RDRAMRD  = 0xC013 // reading from auxilliary 48K
+	RDRAMWR  = 0xC014 // writing to auxilliary 48K
+	RDCXROM  = 0xC015 // using external slot ROM
+	RDAUXZP  = 0xC016 // using auxilliary ZP, stack, & LC
+	RDC3ROM  = 0xC017 // using external slot C3 ROM
+	RD80COL  = 0xC018 // using 80-column memory mapping
+	RDVBLBAR = 0xC019 // not VBL (VBL signal low)
+	RDTEXT   = 0xC01A // using text mode
+	RDMIXED  = 0xC01B // using mixed mode
+	RDPAGE2  = 0xC01C // using text/graphics page2
+	RDHIRES  = 0xC01D // using Hi-res graphics mode
+	RDALTCH  = 0xC01E // using alternate character set ROM
+	RD80VID  = 0xC01F // using 80-column display mode
+	SPEAKER  = 0xC030 // toggle speaker diaphragm
+
+	CLRTEXT  = 0xC050 // enable text-only mode
+	SETTEXT  = 0xC051
+	CLRMIXED = 0xC052 // enable graphics/text mixed mode
+	SETMIXED = 0xC053
+	TXTPAGE1 = 0xC054 // select page1/2 (or page1/1x)
+	TXTPAGE2 = 0xC055
+	CLRHIRES = 0xC056 // enable Hi-res graphics
+	SETHIRES = 0xC057
+
+	SETAN0 = 0xC058 // 4-bit annunciator inputs
+	CLRAN0 = 0xC059
+	SETAN1 = 0xC05A
+	CLRAN1 = 0xC05B
+	SETAN2 = 0xC05C
+	CLRAN2 = 0xC05D
+	SETAN3 = 0xC05E
+	CLRAN3 = 0xC05F
+
+	OPNAPPLE = 0xC061 // open apple (command) key data
+	CLSAPPLE = 0xC062 // closed apple (option) key data
+
+	PDLTRIG = 0xC070 // trigger paddles
+)
+
+// Handle soft switch addresses where both a read and a write has a side
+// effect and the return value is meaningless
+func readWrite(address uint16) bool {
+	switch address {
+	case CLRTEXT:
+		panic("CLRTEXT not implemented")
+	case SETTEXT:
+		return true
+	case TXTPAGE1:
+		return true
+	case TXTPAGE2:
+		return true
+		fmt.Println("TXTPAGE2 not implemented")
+		// panic("TXTPAGE2 not implemented")
+		return true
+	case CLRHIRES:
+		return true
+	case SETHIRES:
+		panic("SETIRES not implemented")
+	default:
+		return false
+	}
+}
+
+func ReadIO(address uint16) uint8 {
+	if readWrite(address) {
+		return 0
+	}
+
+	switch address {
+	case KEYBOARD, STROBE:
+		keyBoardData, strobe := keyboard.Read()
+		if address == KEYBOARD {
+			return keyBoardData
+		} else {
+			keyboard.ResetStrobe()
+			return strobe
+		}
+	case RDCXROM:
+		if UsingExternalSlotRom {
+			return 0x8d
+		} else {
+			return 0x0d
+		}
+	case RD80VID:
+		// using 80-column display mode not implemented
+		return 0x0d
+
+	// 4-bit annunciator inputs
+	case SETAN0, CLRAN0, SETAN1, CLRAN1, SETAN2, CLRAN2, SETAN3, CLRAN3:
+		// Annunciators not implemented
+	case OPNAPPLE:
+		// Open apple key not implemented
+		return 0
+	case CLSAPPLE:
+		// Closed apple key not implemented
+	case RD80COL:
+		// RD80COL not implemented
+		return 0x0d
+	case RDPAGE2:
+		// RDPAGE2 not implemented
+		return 0x0d
+	case RDALTCH:
+		// RDALTCH not implemented
+		return 0x0d
+	case SPEAKER:
+		// Speaker not implemented
+		// Not printing anything since this will generate a lot of noise
+	default:
+		panic(fmt.Sprintf("TODO read %04x\n", address))
+	}
+
+	return 0
+}
+
+func WriteIO(address uint16, value uint8) {
+	if readWrite(address) {
+		return
+	}
+
+	switch address {
+	case STROBE:
+		keyboard.ResetStrobe()
+	case CLRCXROM:
+		MapFirstHalfOfIO()
+	case SETCXROM:
+		MapSecondHalfOfIO()
+	case CLRALTCH:
+		return
+	case SETALTCH:
+		panic("SETALTCH not implemented")
+	case CLR80COL:
+		// CLR80COL not implemented
+		return
+	case SET80COL:
+		// SET80COL not implemented
+	case CLRC3ROM:
+		// CLRC3ROM not implemented
+	case SETC3ROM:
+		// SETC3ROM not implemented
+	default:
+		panic(fmt.Sprintf("TODO write %04x\n", address))
+	}
+
+	return
+}

mmu/mmu.go

@@ -3,53 +3,12 @@ package mmu
 import (
 	"fmt"
 	"io/ioutil"
-	"mos6502go/keyboard"
 	"mos6502go/system"
 )
 
 const RomPath = "apple2e.rom"
 const StackPage = 1
 
-// https://mirrors.apple2.org.za/apple.cabi.net/Languages.Programming/MemoryMap.IIe.64K.128K.txt
-
-const (
-	KEYBOARD = 0xC000 // keyboard data (latched) (RD-only)
-	CLR80COL = 0xC000 // use 80-column memory mapping (WR-only)
-	SET80COL = 0xC001
-	CLRAUXRD = 0xC002 // read from auxilliary 48K
-	SETAUXRD = 0xC003
-	CLRAUXWR = 0xC004 // write to auxilliary 48K
-	SETAUXWR = 0xC005
-	CLRCXROM = 0xC006 // use external slot ROM
-	SETCXROM = 0xC007
-	CLRAUXZP = 0xC008 // use auxilliary ZP, stack, & LC
-	SETAUXZP = 0xC009
-	CLRC3ROM = 0xC00A // use external slot C3 ROM
-	SETC3ROM = 0xC00B
-	CLR80VID = 0xC00C // use 80-column display mode
-	SET80VID = 0xC00D
-	CLRALTCH = 0xC00E // use alternate character set ROM
-	SETALTCH = 0xC00F
-	STROBE   = 0xC010 // strobe (unlatch) keyboard data
-
-	RDLCBNK2 = 0xC011 // reading from LC bank $Dx 2
-	RDLCRAM  = 0xC012 // reading from LC RAM
-	RDRAMRD  = 0xC013 // reading from auxilliary 48K
-	RDRAMWR  = 0xC014 // writing to auxilliary 48K
-	RDCXROM  = 0xC015 // using external slot ROM
-	RDAUXZP  = 0xC016 // using auxilliary ZP, stack, & LC
-	RDC3ROM  = 0xC017 // using external slot C3 ROM
-	RD80COL  = 0xC018 // using 80-column memory mapping
-	RDVBLBAR = 0xC019 // not VBL (VBL signal low)
-	RDTEXT   = 0xC01A // using text mode
-	RDMIXED  = 0xC01B // using mixed mode
-	RDPAGE2  = 0xC01C // using text/graphics page2
-	RDHIRES  = 0xC01D // using Hi-res graphics mode
-	RDALTCH  = 0xC01E // using alternate character set ROM
-	RD80VID  = 0xC01F // using 80-column display mode
-
-)
-
 var PhysicalMemory struct {
 	MainMemory [0xc000]uint8
 	UpperROM   [0x3000]uint8
@@ -59,13 +18,19 @@ var PhysicalMemory struct {
 
 var PageTable [0x100][]uint8
 
+var UsingExternalSlotRom bool
+
 func MapFirstHalfOfIO() {
+	UsingExternalSlotRom = false
+
 	for i := 0x1; i < 0x10; i++ {
 		PageTable[i+0xc0] = PhysicalMemory.RomC1[i*0x100 : i*0x100+0x100]
 	}
 }
 
 func MapSecondHalfOfIO() {
+	UsingExternalSlotRom = true
+
 	for i := 0x1; i < 0x10; i++ {
 		PageTable[i+0xc0] = PhysicalMemory.RomC2[i*0x100 : i*0x100+0x100]
 	}
@@ -121,36 +86,25 @@ func InitRAM() {
 		PageTable[i] = PhysicalMemory.MainMemory[i*0x100 : i*0x100+0x100]
 	}
 
+	UsingExternalSlotRom = true
+
 	return
 }
 
 func ReadMemory(address uint16) uint8 {
 	if (address >= 0xc000) && (address < 0xc100) {
-
+		return ReadIO(address)
-		if (address == KEYBOARD) || (address == STROBE) {
-			keyBoardData, strobe := keyboard.Read()
-			if address == KEYBOARD {
-				return keyBoardData
 	} else {
-				keyboard.ResetStrobe()
-				return strobe
-			}
-		} else if address == RDCXROM {
-			// using external slot ROM not implemented
-			return 0
-		} else if address == RD80VID {
-			// using 80-column display mode not implemented
-			return 0
-		}
-
-		fmt.Printf("TODO read %04x\n", address)
-		return 0
-	}
-
 		return PageTable[address>>8][address&0xff]
 	}
+}
 
 func WriteMemory(address uint16, value uint8) {
+	if (address >= 0xc000) && (address < 0xc100) {
+		WriteIO(address, value)
+		return
+	}
+
 	if system.RunningInterruptTests && address == 0xbffc {
 		oldValue := ReadMemory(address)
 		system.WriteInterruptTestOpenCollector(address, oldValue, value)
@@ -158,19 +112,6 @@ func WriteMemory(address uint16, value uint8) {
 		return
 	}
 
-	if address >= 0xc000 {
-		if address == STROBE {
-			keyboard.ResetStrobe()
-		} else if address == CLRCXROM {
-			MapFirstHalfOfIO()
-		} else if address == SETCXROM {
-			MapSecondHalfOfIO()
-		} else {
-			fmt.Printf("TODO write %04x\n", address)
-		}
-		return
-	}
-
 	PageTable[uint8(address>>8)][uint8(address&0xff)] = value
 
 	if system.RunningFunctionalTests && address == 0x200 {