75 lines
1.9 KiB
Go
75 lines
1.9 KiB
Go
package apple2
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type disketteWoz struct {
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data *fileWoz
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cycleOn uint64 // Cycle when the disk was last turned on
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turning bool
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latch uint8
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position uint32
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cycle uint64
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trackSize uint32
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visibleLatch uint8
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visibleLatchCountDown int8 // The visible latch stores a valid latch reading for 2 bit timings
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}
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func (d *disketteWoz) powerOn(cycle uint64) {
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d.turning = true
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d.cycleOn = cycle
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}
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func (d *disketteWoz) powerOff(_ uint64) {
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d.turning = false
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}
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func (d *disketteWoz) read(quarterTrack int, cycle uint64) uint8 {
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// Count cycles to know how many bits have been read
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cycles := cycle - d.cycle
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deltaBits := cycles / cyclesPerBit // TODO: Use Woz optimal bit timing
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// Process bits from woz
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// TODO: avoid processing too many bits if delta is big
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for i := uint64(0); i < deltaBits; i++ {
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d.position++
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bit := d.data.getBit(d.position, quarterTrack)
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d.latch = (d.latch << 1) + bit
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if d.latch >= 0x80 {
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// Valid byte, store value a bit longer and clear the internal latch
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//fmt.Printf("Valid 0x%.2x\n", d.latch)
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d.visibleLatch = d.latch
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d.visibleLatchCountDown = 1
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d.latch = 0
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} else if d.visibleLatchCountDown > 0 {
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// Continue showing the valid byte
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d.visibleLatchCountDown--
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} else {
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// The valid byte is lost, show the internal latch
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d.visibleLatch = d.latch
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}
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}
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//fmt.Printf("Visible: 0x%.2x, latch: 0x%.2x, bits: %v, cycles: %v\n", d.visibleLatch, d.latch, deltaBits, cycle-d.cycle)
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// Update the internal last cycle without losing the remainder not processed
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d.cycle += deltaBits * cyclesPerBit
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return d.visibleLatch
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}
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func (d *disketteWoz) write(quarterTrack int, value uint8, _ uint64) {
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panic("Write not implemented on woz disk implementation")
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}
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func loadDisquetteWoz(filename string) (*disketteWoz, error) {
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var d disketteWoz
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f, err := loadFileWoz(filename)
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if err != nil {
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return nil, err
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}
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d.data = f
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return &d, nil
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}
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