package izapple2 import ( "fmt" ) /* https://applesaucefdc.com/woz/reference2/ Good explanation of the softswitches and the phases: http://yesterbits.com/media/pubs/AppleOrchard/articles/disk-ii-part-1-1983-apr.pdf "IMW Floppy Disk I/O Controller info" (https://www.brutaldeluxe.fr/documentation/iwm/apple2_IWM_INFO_19840510.pdf) "Understanfing the Apple II, chapter 9" 35 tracks, 16 sectors, 256 bytes NIB: 35 tracks 6656 bytes, 232960 bytes */ const maxHalfTrack = 68 type cardDisk2 struct { cardBase selected int // q5, Only 0 and 1 supported drive [2]cardDisk2Drive dataLatch uint8 q6 bool q7 bool } type cardDisk2Drive struct { diskette diskette power bool // q4 phases uint8 // q3, q2, q1 and q0 with q0 on the LSB. Magnets that are active on the stepper motor tracksStep int // Stepmotor for tracks position. 4 steps per track } const ( diskBitCycle = 4 // There is a dataLatch bit transferred every 4 cycles diskLatchReadCycles = 7 // Loaded data is available for a little more than 7ns diskWriteByteCycle = 32 // Load data to write every 32 cycles diskWriteSelfSyncCycle = 40 // Save $FF every 40 cycles. Self sync is 10 bits: 1111 1111 00 diskMotorStartMs = 150 // Time with the disk spinning to get full speed ) func (c *cardDisk2) assign(a *Apple2, slot int) { // Q1, Q2, Q3 and Q4 phase control soft switches, for i := uint8(0); i < 4; i++ { phase := i c.addCardSoftSwitchR(phase<<1, func(_ *ioC0Page) uint8 { // Update magnets and position drive := &c.drive[c.selected] drive.phases &^= (1 << phase) drive.tracksStep = moveStep(drive.phases, drive.tracksStep) return c.dataLatch // All even addresses return the last dataLatch }, fmt.Sprintf("PHASE%vOFF", phase)) c.addCardSoftSwitchR((phase<<1)+1, func(_ *ioC0Page) uint8 { // Update magnets and position drive := &c.drive[c.selected] drive.phases |= (1 << phase) drive.tracksStep = moveStep(drive.phases, drive.tracksStep) return 0 }, fmt.Sprintf("PHASE%vON", phase)) } // Q4, power switch c.addCardSoftSwitchR(0x8, func(_ *ioC0Page) uint8 { drive := &c.drive[c.selected] if drive.power { drive.power = false c.a.releaseFastMode() if drive.diskette != nil { drive.diskette.powerOff(c.a.cpu.GetCycles()) } } return c.dataLatch }, "Q4DRIVEOFF") c.addCardSoftSwitchR(0x9, func(_ *ioC0Page) uint8 { drive := &c.drive[c.selected] if !drive.power { drive.power = true c.a.requestFastMode() if drive.diskette != nil { drive.diskette.powerOn(c.a.cpu.GetCycles()) } } return 0 }, "Q4DRIVEON") // Q5, drive selecion c.addCardSoftSwitchR(0xA, func(_ *ioC0Page) uint8 { c.selected = 0 return c.dataLatch }, "Q5SELECT1") c.addCardSoftSwitchR(0xB, func(_ *ioC0Page) uint8 { c.selected = 1 return 0 }, "Q5SELECT2") // Q6, Q7 for i := uint8(0xC); i <= 0xF; i++ { iCopy := i c.addCardSoftSwitchR(iCopy, func(_ *ioC0Page) uint8 { return c.softSwitchQ6Q7(iCopy, 0) }, "Q6Q7") c.addCardSoftSwitchW(iCopy, func(_ *ioC0Page, value uint8) { c.softSwitchQ6Q7(iCopy, value) }, "Q6Q7") } c.cardBase.assign(a, slot) } // Q6: shift/load // Q7: read/write func (c *cardDisk2) softSwitchQ6Q7(index uint8, in uint8) uint8 { switch index { case 0xC: // Q6L c.q6 = false case 0xD: // Q6H c.q6 = true case 0xE: // Q7L c.q7 = false case 0xF: // Q7H c.q7 = true } c.processQ6Q7(in) if index&1 == 0 { // All even addresses return the last dataLatch return c.dataLatch } return 0 } func (c *cardDisk2) processQ6Q7(in uint8) { d := &c.drive[c.selected] if d.diskette == nil { return } if !c.q6 { // shift if !c.q7 { // Q6L-Q7L: Read c.dataLatch = d.diskette.read(d.tracksStep, c.a.cpu.GetCycles()) } else { // Q6L-Q7H: Write the dataLatch value to disk. Shift data out d.diskette.write(d.tracksStep, c.dataLatch, c.a.cpu.GetCycles()) } } else { // load if !c.q7 { // Q6H-Q7L: Sense write protect / prewrite state // Bit 7 of the control status register means write protected c.dataLatch = 0 // Never write protected } else { // Q6H-Q7H: Load data into the controller c.dataLatch = in } } if c.dataLatch >= 0x80 { //fmt.Printf("Datalacth: 0x%.2x in cycle %v\n", c.dataLatch, c.a.cpu.GetCycles()) } } /* Stepper motor to position the track. There are a number of group of four magnets. The stepper motor can be thought as a long line of groups of magnets, each group on the same configuration. We call phase each of those magnets. The cog is attracted to the enabled magnets, and can stay aligned to a magnet or between two. Phases (magents): 3 2 1 0 3 2 1 0 3 2 1 0 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 We will consider that the cog would go to the prefferred postion if there is one. Independenly of the previous position. The previous position is only used to know if it goes up or down a full group. */ const ( undefinedPosition = -1 maxStep = 68 * 2 // What is the maximum quarter tracks a DiskII can go? stepsPerGroup = 8 stepsPerTrack = 4 ) var cogPositions = []int{ undefinedPosition, // 0000, phases active 0, // 0001 2, // 0010 1, // 0011 4, // 0100 undefinedPosition, // 0101 3, // 0110 2, // 0111 6, // 1000 7, // 1001 undefinedPosition, // 1010 0, // 1011 5, // 1100 6, // 1101 4, // 1110 undefinedPosition, // 1111 } func moveStep(phases uint8, prevStep int) int { //fmt.Printf("magnets: 0x%x\n", phases) cogPosition := cogPositions[phases] if cogPosition == undefinedPosition { // Don't move if magnets don't push on a defined direction. return prevStep } prevPosition := prevStep % stepsPerGroup // Direction, step in the current group of magnets. delta := cogPosition - prevPosition if delta < 0 { delta = delta + stepsPerGroup } var nextStep int if delta < 4 { // Steps up nextStep = prevStep + delta if nextStep > maxStep { nextStep = maxStep } } else if delta == 4 { // Don't move if magnets push on the oposite direction nextStep = prevStep } else { // delta > 4 // Steps down nextStep = prevStep + delta - stepsPerGroup if nextStep < 0 { nextStep = 0 } } return nextStep } func (d *cardDisk2Drive) insertDiskette(dt diskette) { d.diskette = dt }