Boots DOS 3.3 using nib format

apple2/apple2.go

@@ -32,9 +32,13 @@ func NewApple2(romFile string) *Apple2 {
 }
 
 // AddDisk2 insterts a DiskII controller on slot 6
-func (a *Apple2) AddDisk2(diskRomFile string) {
+func (a *Apple2) AddDisk2(diskRomFile string, diskImage string) {
 	d := newCardDisk2(diskRomFile)
 	d.cardBase.insert(a, 6)
+
+	if diskImage != "" {
+		d.drive[0].loadDisk(diskImage)
+	}
 }
 
 // Run starts the Apple2 emulation

apple2/cardDisk2.go

@@ -2,7 +2,6 @@ package apple2
 
 import (
 	"bufio"
-	"fmt"
 	"os"
 )
 
@@ -10,14 +9,29 @@ import (
 https://applesaucefdc.com/woz/reference2/
 Good explanation of the softswitches and the phases:
 http://yesterbits.com/media/pubs/AppleOrchard/articles/disk-ii-part-1-1983-apr.pdf
+
+35 tracks, 16 sectors, 256 bytes
+NIB: 35 tracks 6656 bytes, 232960 bytes
+
 */
+const maxHalfTrack = 68
+const bytesPerTrack = 6656
+const nibImageSize = 35 * bytesPerTrack
 
 type cardDisk2 struct {
 	cardBase
-	phases    [4]bool
+	selected int // Only 0 and 1 supported
-	power     [2]bool
+	drive    [2]cardDisk2Drive
-	selected  int // Only 0 and 1 supported
+}
-	writeMode bool
+
+type cardDisk2Drive struct {
+	isLoaded     bool
+	currentPhase int
+	power        bool
+	writeMode    bool
+	halfTrack    int
+	position     int
+	data         *[]uint8
 }
 
 // type softSwitchR func(io *ioC0Page) uint8
@@ -27,73 +41,103 @@ func newCardDisk2(filename string) *cardDisk2 {
 	c.rom = loadCardRom(filename)
 
 	// Phase control soft switches
+	// Lazy emulation. It only checks for phases on and move the head
+	// up or down depending on the previous phase.
 	for i := 0; i < 4; i++ {
-		c.ssr[i<<1] = func(_ *ioC0Page) uint8 {
+		func(phase int) {
-			fmt.Printf("DISKII: Phase %v off\n", i)
+			c.ssr[phase<<1] = func(_ *ioC0Page) uint8 {
-			return 0
+				//fmt.Printf("DISKII: Phase %v off\n", phase)
-		}
+				return 0
-		c.ssr[(i<<1)+1] = func(_ *ioC0Page) uint8 {
+			}
-			fmt.Printf("DISKII: Phase %v on\n", i)
+			c.ssr[(phase<<1)+1] = func(_ *ioC0Page) uint8 {
-			return 0
+				//fmt.Printf("DISKII: Phase %v on\n", phase)
-		}
+				halfTrack := c.drive[c.selected].halfTrack
+				delta := (phase - c.drive[c.selected].currentPhase + 4) % 4
+				switch delta {
+				case 1: // Up
+					halfTrack++
+				case 2: // Illegal, let's say up
+					halfTrack++
+				case 3: // Down
+					halfTrack--
+				case 0: // No chamge
+				}
+
+				if halfTrack > maxHalfTrack {
+					halfTrack = maxHalfTrack
+				} else if halfTrack < 0 {
+					halfTrack = 0
+				}
+				c.drive[c.selected].halfTrack = halfTrack
+				c.drive[c.selected].currentPhase = phase
+				//fmt.Printf("DISKII: Current halftrack is %v\n", halfTrack)
+				return 0
+			}
+		}(i)
 	}
 
 	// Other soft switches
 	c.ssr[0x8] = func(_ *ioC0Page) uint8 {
-		c.power[c.selected] = false
+		c.drive[c.selected].power = false
-		fmt.Printf("DISKII: Disk %v is off\n", c.selected)
+		//fmt.Printf("DISKII: Disk %v is off\n", c.selected)
 		return 0
 	}
 	c.ssr[0x9] = func(_ *ioC0Page) uint8 {
-		c.power[c.selected] = true
+		c.drive[c.selected].power = true
-		fmt.Printf("DISKII: Disk %v is on\n", c.selected)
+		//fmt.Printf("DISKII: Disk %v is on\n", c.selected)
 		return 0
 	}
 	c.ssr[0xA] = func(_ *ioC0Page) uint8 {
 		c.selected = 0
-		fmt.Printf("DISKII: Disk %v selected\n", c.selected)
+		//fmt.Printf("DISKII: Disk %v selected\n", c.selected)
 		return 0
 	}
 	c.ssr[0xB] = func(_ *ioC0Page) uint8 {
 		c.selected = 1
-		fmt.Printf("DISKII: Disk %v selected\n", c.selected)
+		//fmt.Printf("DISKII: Disk %v selected\n", c.selected)
 		return 0
 	}
 
-	var i uint8
 	// Q6L
 	c.ssr[0xC] = func(_ *ioC0Page) uint8 {
-		fmt.Printf("DISKII: Reading\n")
+		//fmt.Printf("DISKII: Reading\n")
-		i++
+		drive := &c.drive[c.selected]
-		return i
+		if drive.isLoaded {
+			track := drive.halfTrack / 2
+			data := *drive.data
+			value := data[track*bytesPerTrack+drive.position]
+			//fmt.Printf("DISKII: Reading value 0x%02v from track %v, position %v\n", value, track, drive.position)
+			drive.position = (drive.position + 1) % bytesPerTrack
+			return value
+		} else {
+			return 0
+		}
 	}
 
 	c.ssw[0xC] = func(_ *ioC0Page, value uint8) {
-		fmt.Printf("DISKII: Writing the value 0x%02x\n", value)
+		//fmt.Printf("DISKII: Writing the value 0x%02x\n", value)
 	}
 
 	// Q6H
 	c.ssr[0xD] = func(_ *ioC0Page) uint8 {
-		c.writeMode = false
+		c.drive[c.selected].writeMode = false
-		fmt.Printf("DISKII: Sense write protection\n")
+		//fmt.Printf("DISKII: Sense write protection\n")
 		return 0
 	}
 
 	// Q7L
 	c.ssr[0xE] = func(_ *ioC0Page) uint8 {
-		c.writeMode = false
+		c.drive[c.selected].writeMode = false
-		fmt.Printf("DISKII: Set read mode\n")
+		//fmt.Printf("DISKII: Set read mode\n")
 		return 0
 	}
 
 	// Q7H
 	c.ssr[0xF] = func(_ *ioC0Page) uint8 {
-		c.writeMode = true
+		c.drive[c.selected].writeMode = true
-		fmt.Printf("DISKII: Set write mode\n")
+		//fmt.Printf("DISKII: Set write mode\n")
 		return 0
 	}
-	// TODO: missing C, D, E, and F
-
 	return &c
 }
 
@@ -131,3 +175,28 @@ func loadCardRom(filename string) []memoryPage {
 
 	return memPages
 }
+
+func (d *cardDisk2Drive) loadDisk(filename string) {
+	f, err := os.Open(filename)
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+
+	stats, statsErr := f.Stat()
+	if statsErr != nil {
+		panic(err)
+	}
+
+	size := stats.Size()
+	if size != nibImageSize {
+		panic("Disk size with nib format has to be 232960 bytes")
+	}
+
+	bytes := make([]uint8, size)
+	buf := bufio.NewReader(f)
+	buf.Read(bytes)
+
+	d.data = &bytes
+	d.isLoaded = true
+}

apple2/ioC0Page.go

@@ -72,7 +72,8 @@ func (p *ioC0Page) Peek(address uint8) uint8 {
 	//fmt.Printf("Peek on $C0%02x ", address)
 	ss := p.softSwitchesR[address]
 	if ss == nil {
-		panic(fmt.Sprintf("Unknown softswitch on read to 0xC0%02x", address))
+		//panic(fmt.Sprintf("Unknown softswitch on read to 0xC0%02x", address))
+		return 0
 	}
 
 	return ss(p)
@@ -82,7 +83,8 @@ func (p *ioC0Page) Poke(address uint8, value uint8) {
 	//fmt.Printf("Poke on $C0%02x with %02x ", address, value)
 	ss := p.softSwitchesW[address]
 	if ss == nil {
-		panic(fmt.Sprintf("Unknown softswitch on write to 0xC0%02x", address))
+		//panic(fmt.Sprintf("Unknown softswitch on write to 0xC0%02x", address))
+		return
 	}
 	ss(p, value)
 }

apple2/unassignedPage.go

@@ -1,18 +1,16 @@
 package apple2
 
-import "fmt"
-
 type unassignedPage struct {
 	page uint8
 }
 
 func (p *unassignedPage) Peek(address uint8) uint8 {
-	fmt.Printf("Read on address 0x%02x%02x\n", p.page, address)
+	//fmt.Printf("Read on address 0x%02x%02x\n", p.page, address)
 	//panic(address)
 	return 0xdd
 }
 
 func (p *unassignedPage) Poke(address uint8, value uint8) {
-	fmt.Printf("Write on address 0x%02x%02x\n", p.page, address)
+	//fmt.Printf("Write on address 0x%02x%02x\n", p.page, address)
 	//panic(address)
 }

main.go

@@ -6,10 +6,11 @@ func main() {
 	//romFile := "apple2/romdumps/Apple2.rom"
 	romFile := "apple2/romdumps/Apple2_Plus.rom"
 	//romFile := "apple2/romdumps/Apple2e.rom"
-	//disk2RomFile := "apple2/romdumps/DISK2.rom"
+	disk2RomFile := "apple2/romdumps/DISK2.rom"
+	diskImage := "../dos33.nib"
 
-	log := true
+	log := false
 	a := apple2.NewApple2(romFile)
-	//a.AddDisk2(disk2RomFile)
+	a.AddDisk2(disk2RomFile, diskImage)
 	a.Run(log)
 }