izapple2/apple2/cardDisk2.go

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package apple2
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import (
"bufio"
"os"
)
/*
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
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35 tracks, 16 sectors, 256 bytes
NIB: 35 tracks 6656 bytes, 232960 bytes
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*/
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const maxHalfTrack = 68
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type cardDisk2 struct {
cardBase
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selected int // Only 0 and 1 supported
drive [2]cardDisk2Drive
}
type cardDisk2Drive struct {
diskette *diskette16sector
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currentPhase int
power bool
writeMode bool
halfTrack int
position int
}
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// type softSwitchR func(io *ioC0Page) uint8
func newCardDisk2(filename string) *cardDisk2 {
var c cardDisk2
c.rom = loadCardRom(filename)
// Phase control soft switches
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// Lazy emulation. It only checks for phases on and move the head
// up or down depending on the previous phase.
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for i := 0; i < 4; i++ {
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func(phase int) {
c.ssr[phase<<1] = func(_ *ioC0Page) uint8 {
//fmt.Printf("DISKII: Phase %v off\n", phase)
return 0
}
c.ssr[(phase<<1)+1] = func(_ *ioC0Page) uint8 {
//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)
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}
// Other soft switches
c.ssr[0x8] = func(_ *ioC0Page) uint8 {
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c.drive[c.selected].power = false
//fmt.Printf("DISKII: Disk %v is off\n", c.selected)
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return 0
}
c.ssr[0x9] = func(_ *ioC0Page) uint8 {
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c.drive[c.selected].power = true
//fmt.Printf("DISKII: Disk %v is on\n", c.selected)
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return 0
}
c.ssr[0xA] = func(_ *ioC0Page) uint8 {
c.selected = 0
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//fmt.Printf("DISKII: Disk %v selected\n", c.selected)
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return 0
}
c.ssr[0xB] = func(_ *ioC0Page) uint8 {
c.selected = 1
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//fmt.Printf("DISKII: Disk %v selected\n", c.selected)
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return 0
}
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// Q6L
c.ssr[0xC] = func(_ *ioC0Page) uint8 {
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//fmt.Printf("DISKII: Reading\n")
drive := &c.drive[c.selected]
if drive.diskette == nil {
return 0xff
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}
track := drive.halfTrack / 2
value, newPosition := drive.diskette.read(track, drive.position)
drive.position = newPosition
//fmt.Printf("DISKII: Reading value 0x%02v from track %v, position %v\n", value, track, drive.position)
return value
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}
c.ssw[0xC] = func(_ *ioC0Page, value uint8) {
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//fmt.Printf("DISKII: Writing the value 0x%02x\n", value)
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}
// Q6H
c.ssr[0xD] = func(_ *ioC0Page) uint8 {
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c.drive[c.selected].writeMode = false
//fmt.Printf("DISKII: Sense write protection\n")
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return 0
}
// Q7L
c.ssr[0xE] = func(_ *ioC0Page) uint8 {
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c.drive[c.selected].writeMode = false
//fmt.Printf("DISKII: Set read mode\n")
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return 0
}
// Q7H
c.ssr[0xF] = func(_ *ioC0Page) uint8 {
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c.drive[c.selected].writeMode = true
//fmt.Printf("DISKII: Set write mode\n")
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return 0
}
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return &c
}
func loadCardRom(filename string) []memoryPage {
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()
bytes := make([]byte, size)
buf := bufio.NewReader(f)
buf.Read(bytes)
pages := size / 256
if (size % 256) > 0 {
pages++
}
rom := make([]romPage, pages)
for i := int64(0); i < size; i++ {
rom[i>>8].burn(uint8(i), bytes[i])
}
memPages := make([]memoryPage, pages)
for i := range rom {
memPages[i] = &rom[i]
}
return memPages
}
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func (d *cardDisk2Drive) insertDiskette(dt *diskette16sector) {
d.diskette = dt
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}