izapple2/cardDisk2.go

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package apple2
import (
"encoding/binary"
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"fmt"
"io"
)
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/*
https://applesaucefdc.com/woz/reference2/
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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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"IMW Floppy Disk I/O Controller info" (https://www.brutaldeluxe.fr/documentation/iwm/apple2_IWM_INFO_19840510.pdf)
"Understanfing the Apple II, chapter 9"
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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
selected int // q5, Only 0 and 1 supported
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drive [2]cardDisk2Drive
dataLatch uint8
q6 bool
q7 bool
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}
type cardDisk2Drive struct {
diskette diskette
power bool // q4
phases uint8 // q3, q2, q1 and q0 with q0 on the LSB. Magnets that are active on the stepper motor
tracksStep int // Stepmotor for tracks position. 4 steps per track
}
const (
diskBitCycle = 4 // There is a dataLatch bit transferred every 4 cycles
diskLatchReadCycles = 7 // Loaded data is available for a little more than 7ns
diskWriteByteCycle = 32 // Load data to write every 32 cycles
diskWriteSelfSyncCycle = 40 // Save $FF every 40 cycles. Self sync is 10 bits: 1111 1111 00
diskMotorStartMs = 150 // Time with the disk spinning to get full speed
)
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func (c *cardDisk2) assign(a *Apple2, slot int) {
// Q1, Q2, Q3 and Q4 phase control soft switches,
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for i := uint8(0); i < 4; i++ {
phase := i
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c.addCardSoftSwitchR(phase<<1, func(_ *ioC0Page) uint8 {
// Update magnets and position
drive := &c.drive[c.selected]
drive.phases &^= (1 << phase)
drive.tracksStep = moveStep(drive.phases, drive.tracksStep)
return c.dataLatch // All even addresses return the last dataLatch
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}, fmt.Sprintf("PHASE%vOFF", phase))
c.addCardSoftSwitchR((phase<<1)+1, func(_ *ioC0Page) uint8 {
// Update magnets and position
drive := &c.drive[c.selected]
drive.phases |= (1 << phase)
drive.tracksStep = moveStep(drive.phases, drive.tracksStep)
return 0
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}, fmt.Sprintf("PHASE%vOFF", phase))
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}
// Q4, power switch
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c.addCardSoftSwitchR(0x8, func(_ *ioC0Page) uint8 {
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drive := &c.drive[c.selected]
if drive.power {
drive.power = false
c.a.releaseFastMode()
if drive.diskette != nil {
drive.diskette.powerOff(c.a.cpu.GetCycles())
}
}
return c.dataLatch
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}, "Q4DRIVEOFF")
c.addCardSoftSwitchR(0x9, func(_ *ioC0Page) uint8 {
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drive := &c.drive[c.selected]
if !drive.power {
drive.power = true
c.a.requestFastMode()
if drive.diskette != nil {
drive.diskette.powerOn(c.a.cpu.GetCycles())
}
}
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return 0
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}, "Q4DRIVEON")
// Q5, drive selecion
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c.addCardSoftSwitchR(0xA, func(_ *ioC0Page) uint8 {
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c.selected = 0
return c.dataLatch
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}, "Q5SELECT1")
c.addCardSoftSwitchR(0xB, func(_ *ioC0Page) uint8 {
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c.selected = 1
return 0
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}, "Q5SELECT2")
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// Q6, Q7
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for i := uint8(0xC); i <= 0xF; i++ {
iCopy := i
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c.addCardSoftSwitchR(iCopy, func(_ *ioC0Page) uint8 {
return c.softSwitchQ6Q7(iCopy, 0)
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}, "Q6Q7")
c.addCardSoftSwitchW(iCopy, func(_ *ioC0Page, value uint8) {
c.softSwitchQ6Q7(iCopy, value)
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}, "Q6Q7")
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}
c.cardBase.assign(a, slot)
}
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// Q6: shift/load
// Q7: read/write
func (c *cardDisk2) softSwitchQ6Q7(index uint8, in uint8) uint8 {
switch index {
case 0xC: // Q6L
c.q6 = false
case 0xD: // Q6H
c.q6 = true
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case 0xE: // Q7L
c.q7 = false
case 0xF: // Q7H
c.q7 = true
}
c.processQ6Q7(in)
if index&1 == 0 {
// All even addresses return the last dataLatch
return c.dataLatch
}
return 0
}
func (c *cardDisk2) processQ6Q7(in uint8) {
d := &c.drive[c.selected]
if d.diskette == nil {
return
}
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if !c.q6 { // shift
if !c.q7 { // Q6L-Q7L: Read
c.dataLatch = d.diskette.read(d.tracksStep, c.a.cpu.GetCycles())
} else { // Q6L-Q7H: Write the dataLatch value to disk. Shift data out
d.diskette.write(d.tracksStep, c.dataLatch, c.a.cpu.GetCycles())
}
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} else { // load
if !c.q7 { // Q6H-Q7L: Sense write protect / prewrite state
// Bit 7 of the control status register means write protected
c.dataLatch = 0 // Never write protected
} else { // Q6H-Q7H: Load data into the controller
c.dataLatch = in
}
}
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if c.dataLatch >= 0x80 {
//fmt.Printf("Datalacth: 0x%.2x in cycle %v\n", c.dataLatch, c.a.cpu.GetCycles())
}
}
/*
Stepper motor to position the track.
There are a number of group of four magnets. The stepper motor can be thought as a long
line of groups of magnets, each group on the same configuration. We call phase each of those
magnets. The cog is attracted to the enabled magnets, and can stay aligned to a magnet or
between two.
Phases (magents): 3 2 1 0 3 2 1 0 3 2 1 0
Cog direction (step withn a group): 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
We will consider that the cog would go to the prefferred postion if there is one. Independenly
of the previous position. The previous position is only used to know if it goes up or down
a full group.
*/
const (
undefinedPosition = -1
maxStep = 68 * 2 // What is the maximum quarter tracks a DiskII can go?
stepsPerGroup = 8
stepsPerTrack = 4
)
var cogPositions = []int{
undefinedPosition, // 0000, phases active
0, // 0001
2, // 0010
1, // 0011
4, // 0100
undefinedPosition, // 0101
3, // 0110
2, // 0111
6, // 1000
7, // 1001
undefinedPosition, // 1010
0, // 1011
5, // 1100
6, // 1101
4, // 1110
undefinedPosition, // 1111
}
func moveStep(phases uint8, prevStep int) int {
//fmt.Printf("magnets: 0x%x\n", phases)
cogPosition := cogPositions[phases]
if cogPosition == undefinedPosition {
// Don't move if magnets don't push on a defined direction.
return prevStep
}
prevPosition := prevStep % stepsPerGroup // Direction, step in the current group of magnets.
delta := cogPosition - prevPosition
if delta < 0 {
delta = delta + stepsPerGroup
}
var nextStep int
if delta < 4 {
// Steps up
nextStep = prevStep + delta
if nextStep > maxStep {
nextStep = maxStep
}
} else if delta == 4 {
// Don't move if magnets push on the oposite direction
nextStep = prevStep
} else { // delta > 4
// Steps down
nextStep = prevStep + delta - stepsPerGroup
if nextStep < 0 {
nextStep = 0
}
}
return nextStep
}
func (d *cardDisk2Drive) insertDiskette(dt diskette) {
d.diskette = dt
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}
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func (c *cardDisk2) save(w io.Writer) error {
err := binary.Write(w, binary.BigEndian, c.selected)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, c.dataLatch)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, c.q6)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, c.q7)
if err != nil {
return err
}
err = c.drive[0].save(w)
if err != nil {
return err
}
err = c.drive[1].save(w)
if err != nil {
return err
}
return c.cardBase.save(w)
}
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func (c *cardDisk2) load(r io.Reader) error {
err := binary.Read(r, binary.BigEndian, &c.selected)
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &c.dataLatch)
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &c.q6)
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &c.q7)
if err != nil {
return err
}
err = c.drive[0].load(r)
if err != nil {
return err
}
err = c.drive[1].load(r)
if err != nil {
return err
}
return c.cardBase.load(r)
}
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func (d *cardDisk2Drive) save(w io.Writer) error {
err := binary.Write(w, binary.BigEndian, d.power)
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if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, d.phases)
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if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, d.tracksStep)
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if err != nil {
return err
}
return nil
}
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func (d *cardDisk2Drive) load(r io.Reader) error {
err := binary.Read(r, binary.BigEndian, &d.power)
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if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &d.phases)
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if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &d.tracksStep)
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if err != nil {
return err
}
return nil
}