izapple2/cardDisk2SequencerDrive.go
2022-02-26 00:05:09 +01:00

103 lines
2.3 KiB
Go

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