mirror of
https://github.com/ivanizag/izapple2.git
synced 2024-10-31 20:09:02 +00:00
103 lines
2.3 KiB
Go
103 lines
2.3 KiB
Go
package izapple2
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import (
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"errors"
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"math/rand"
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"github.com/ivanizag/izapple2/component"
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"github.com/ivanizag/izapple2/storage"
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)
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type cardDisk2SequencerDrive struct {
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data *storage.FileWoz
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enabled bool
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writeProtected bool
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currentQuarterTrack int
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position uint32 // Current position on the track
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positionMax uint32 // As tracks may have different lengths position is related of positionMax of the las track
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mc3470Buffer uint8 // Four bit buffer to detect weak bits and to add latency
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}
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func (d *cardDisk2SequencerDrive) insertDiskette(filename string) error {
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data, writeable, err := LoadResource(filename)
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if err != nil {
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return err
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}
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f, err := storage.NewFileWoz(data)
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if err != nil {
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return err
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}
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// Discard not supported features
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if f.Info.DiskType != 1 {
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return errors.New("only 5.25 disks are supported")
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}
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if f.Info.BootSectorFormat == 2 { // Info not available in WOZ 1.0
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return errors.New("woz 13 sector disks are not supported")
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}
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d.data = f
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d.writeProtected = !writeable
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return nil
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}
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func (d *cardDisk2SequencerDrive) enable(enabled bool) {
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d.enabled = enabled
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}
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func (d *cardDisk2SequencerDrive) moveHead(q0, q1, q2, q3 bool, trackTracer trackTracer) {
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if !d.enabled {
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return
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}
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phases := component.PinsToByte([8]bool{
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q0, q1, q2, q3,
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false, false, false, false,
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})
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d.currentQuarterTrack = moveDriveStepper(phases, d.currentQuarterTrack)
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if trackTracer != nil {
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trackTracer.traceTrack(d.currentQuarterTrack)
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}
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}
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func (d *cardDisk2SequencerDrive) readPulse() bool {
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if !d.enabled || d.data == nil {
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return false
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}
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// Get next bit taking into account the MC3470 latency and weak bits
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var fluxBit bool
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fluxBit, d.position, d.positionMax = d.data.GetNextBitAndPosition(
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d.position,
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d.positionMax,
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d.currentQuarterTrack)
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d.mc3470Buffer = (d.mc3470Buffer << 1) & 0x0f
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if fluxBit {
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d.mc3470Buffer++
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}
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bit := ((d.mc3470Buffer >> 1) & 0x1) != 0 // Use the previous to last bit to add latency
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if d.mc3470Buffer == 0 && rand.Intn(100) < 30 {
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// Four consecutive zeros. It'a a fake bit.
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// Output a random value. 70% zero, 30% one
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bit = true
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}
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return bit
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}
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func (d *cardDisk2SequencerDrive) writePulse(value bool) {
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if d.writeProtected || !d.enabled || d.data == nil {
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return
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}
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d.data.SetBit(
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value,
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d.position,
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d.positionMax,
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d.currentQuarterTrack)
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}
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