249 lines
6.4 KiB
Go
249 lines
6.4 KiB
Go
package izapple2
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import (
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"fmt"
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)
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/*
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https://applesaucefdc.com/woz/reference2/
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Good explanation of the softswitches and the phases:
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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)
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"Understanfing the Apple II, chapter 9"
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35 tracks, 16 sectors, 256 bytes
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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 {
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cardBase
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selected int // q5, Only 0 and 1 supported
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drive [2]cardDisk2Drive
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dataLatch uint8
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q6 bool
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q7 bool
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}
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type cardDisk2Drive struct {
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diskette diskette
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power bool // q4
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phases uint8 // q3, q2, q1 and q0 with q0 on the LSB. Magnets that are active on the stepper motor
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tracksStep int // Stepmotor for tracks position. 4 steps per track
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}
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const (
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diskBitCycle = 4 // There is a dataLatch bit transferred every 4 cycles
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diskLatchReadCycles = 7 // Loaded data is available for a little more than 7ns
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diskWriteByteCycle = 32 // Load data to write every 32 cycles
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diskWriteSelfSyncCycle = 40 // Save $FF every 40 cycles. Self sync is 10 bits: 1111 1111 00
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diskMotorStartMs = 150 // Time with the disk spinning to get full speed
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)
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func (c *cardDisk2) assign(a *Apple2, slot int) {
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// Q1, Q2, Q3 and Q4 phase control soft switches,
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for i := uint8(0); i < 4; i++ {
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phase := i
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c.addCardSoftSwitchR(phase<<1, func(_ *ioC0Page) uint8 {
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// Update magnets and position
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drive := &c.drive[c.selected]
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drive.phases &^= (1 << phase)
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drive.tracksStep = moveStep(drive.phases, drive.tracksStep)
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return c.dataLatch // All even addresses return the last dataLatch
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}, fmt.Sprintf("PHASE%vOFF", phase))
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c.addCardSoftSwitchR((phase<<1)+1, func(_ *ioC0Page) uint8 {
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// Update magnets and position
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drive := &c.drive[c.selected]
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drive.phases |= (1 << phase)
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drive.tracksStep = moveStep(drive.phases, drive.tracksStep)
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return 0
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}, fmt.Sprintf("PHASE%vON", phase))
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}
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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]
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if drive.power {
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drive.power = false
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c.a.releaseFastMode()
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if drive.diskette != nil {
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drive.diskette.powerOff(c.a.cpu.GetCycles())
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}
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}
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return c.dataLatch
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}, "Q4DRIVEOFF")
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c.addCardSoftSwitchR(0x9, func(_ *ioC0Page) uint8 {
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drive := &c.drive[c.selected]
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if !drive.power {
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drive.power = true
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c.a.requestFastMode()
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if drive.diskette != nil {
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drive.diskette.powerOn(c.a.cpu.GetCycles())
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}
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}
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return 0
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}, "Q4DRIVEON")
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// Q5, drive selecion
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c.addCardSoftSwitchR(0xA, func(_ *ioC0Page) uint8 {
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c.selected = 0
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return c.dataLatch
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}, "Q5SELECT1")
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c.addCardSoftSwitchR(0xB, func(_ *ioC0Page) uint8 {
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c.selected = 1
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return 0
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}, "Q5SELECT2")
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// Q6, Q7
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for i := uint8(0xC); i <= 0xF; i++ {
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iCopy := i
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c.addCardSoftSwitchR(iCopy, func(_ *ioC0Page) uint8 {
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return c.softSwitchQ6Q7(iCopy, 0)
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}, "Q6Q7")
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c.addCardSoftSwitchW(iCopy, func(_ *ioC0Page, value uint8) {
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c.softSwitchQ6Q7(iCopy, value)
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}, "Q6Q7")
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}
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c.cardBase.assign(a, slot)
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}
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// Q6: shift/load
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// Q7: read/write
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func (c *cardDisk2) softSwitchQ6Q7(index uint8, in uint8) uint8 {
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switch index {
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case 0xC: // Q6L
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c.q6 = false
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case 0xD: // Q6H
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c.q6 = true
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case 0xE: // Q7L
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c.q7 = false
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case 0xF: // Q7H
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c.q7 = true
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}
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c.processQ6Q7(in)
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if index&1 == 0 {
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// All even addresses return the last dataLatch
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return c.dataLatch
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}
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return 0
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}
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func (c *cardDisk2) processQ6Q7(in uint8) {
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d := &c.drive[c.selected]
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if d.diskette == nil {
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return
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}
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if !c.q6 { // shift
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if !c.q7 { // Q6L-Q7L: Read
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c.dataLatch = d.diskette.read(d.tracksStep, c.a.cpu.GetCycles())
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} else { // Q6L-Q7H: Write the dataLatch value to disk. Shift data out
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d.diskette.write(d.tracksStep, c.dataLatch, c.a.cpu.GetCycles())
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}
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} else { // load
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if !c.q7 { // Q6H-Q7L: Sense write protect / prewrite state
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// Bit 7 of the control status register means write protected
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c.dataLatch = 0 // Never write protected
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} else { // Q6H-Q7H: Load data into the controller
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c.dataLatch = in
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}
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}
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if c.dataLatch >= 0x80 {
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//fmt.Printf("Datalacth: 0x%.2x in cycle %v\n", c.dataLatch, c.a.cpu.GetCycles())
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}
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}
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/*
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Stepper motor to position the track.
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There are a number of group of four magnets. The stepper motor can be thought as a long
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line of groups of magnets, each group on the same configuration. We call phase each of those
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magnets. The cog is attracted to the enabled magnets, and can stay aligned to a magnet or
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between two.
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Phases (magents): 3 2 1 0 3 2 1 0 3 2 1 0
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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
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We will consider that the cog would go to the prefferred postion if there is one. Independenly
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of the previous position. The previous position is only used to know if it goes up or down
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a full group.
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*/
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const (
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undefinedPosition = -1
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maxStep = 68 * 2 // What is the maximum quarter tracks a DiskII can go?
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stepsPerGroup = 8
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stepsPerTrack = 4
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)
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var cogPositions = []int{
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undefinedPosition, // 0000, phases active
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0, // 0001
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2, // 0010
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1, // 0011
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4, // 0100
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undefinedPosition, // 0101
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3, // 0110
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2, // 0111
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6, // 1000
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7, // 1001
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undefinedPosition, // 1010
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0, // 1011
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5, // 1100
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6, // 1101
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4, // 1110
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undefinedPosition, // 1111
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}
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func moveStep(phases uint8, prevStep int) int {
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//fmt.Printf("magnets: 0x%x\n", phases)
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cogPosition := cogPositions[phases]
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if cogPosition == undefinedPosition {
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// Don't move if magnets don't push on a defined direction.
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return prevStep
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}
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prevPosition := prevStep % stepsPerGroup // Direction, step in the current group of magnets.
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delta := cogPosition - prevPosition
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if delta < 0 {
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delta = delta + stepsPerGroup
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}
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var nextStep int
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if delta < 4 {
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// Steps up
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nextStep = prevStep + delta
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if nextStep > maxStep {
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nextStep = maxStep
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}
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} else if delta == 4 {
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// Don't move if magnets push on the oposite direction
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nextStep = prevStep
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} else { // delta > 4
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// Steps down
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nextStep = prevStep + delta - stepsPerGroup
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if nextStep < 0 {
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nextStep = 0
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}
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}
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return nextStep
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}
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func (d *cardDisk2Drive) insertDiskette(dt diskette) {
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d.diskette = dt
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}
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