mirror of
https://github.com/ivanizag/izapple2.git
synced 2024-10-31 20:09:02 +00:00
41 lines
1.3 KiB
Go
41 lines
1.3 KiB
Go
package storage
|
|
|
|
type diskette16sectorTimed struct {
|
|
nib *fileNib
|
|
cycleOn uint64 // Cycle when the disk was last turned on
|
|
}
|
|
|
|
func (d *diskette16sectorTimed) PowerOn(cycle uint64) {
|
|
d.cycleOn = cycle
|
|
}
|
|
func (d *diskette16sectorTimed) PowerOff(_ uint64) {
|
|
// Not needed
|
|
}
|
|
|
|
func (d *diskette16sectorTimed) getBitPositionInTrack(cycle uint64) int {
|
|
// Calculate how long the disk has been spinning. We move one bit every 4 cycles.
|
|
// In this implementation we don't take into account how long the motor takes to be at full speed.
|
|
cycles := cycle - d.cycleOn
|
|
position := cycles / cyclesPerBit
|
|
return int(position % (8 * nibBytesPerTrack)) // Ignore full turns
|
|
}
|
|
|
|
func (d *diskette16sectorTimed) Read(quarterTrack int, cycle uint64) uint8 {
|
|
track := d.nib.track[quarterTrack/4]
|
|
bitPosition := d.getBitPositionInTrack(cycle)
|
|
bytePosition := bitPosition / 8
|
|
shift := uint(bitPosition % 8)
|
|
if shift == 1 {
|
|
// We continue having the unshifted byte for a little longer (4 cycles)
|
|
shift = 0
|
|
}
|
|
value := track[bytePosition]
|
|
value >>= shift
|
|
//fmt.Printf("%v, %v, %v, %x\n", bitPosition, shift, bytePosition, uint8(value))
|
|
return value
|
|
}
|
|
|
|
func (d *diskette16sectorTimed) Write(quarterTrack int, value uint8, _ uint64) {
|
|
panic("Write not implemented on time based disk implementation")
|
|
}
|