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apple2js
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Split drivers into different files 

Before, all of the disk drivers were in the `disk2.ts` file. With this
change, they are now in separate files with a common `types.ts` file
for shared types. Now, none of the drives depend on the `disk2.ts`
except the WOZ driver that needs access to the sequencer rom. (This
may be moved in a future refactoring.)
This commit is contained in:
Ian Flanigan 2022-09-24 09:45:46 +02:00
parent 630a3e9d38
commit a7bf5d025d
No known key found for this signature in database
GPG Key ID: 035F657DAE4AE7EC
6 changed files with 521 additions and 495 deletions
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503
js/cards/disk2.ts
View File

@ -2,7 +2,6 @@ import { base64_encode } from '../base64';
import type {
byte,
Card,
nibble,
ReadonlyUint8Array
} from '../types';
@ -10,7 +9,7 @@ import {
DISK_PROCESSED, DriveNumber, DRIVE_NUMBERS, FloppyDisk,
FloppyFormat, FormatWorkerMessage,
FormatWorkerResponse, isNibbleDisk, isNoFloppyDisk, isWozDisk, JSONDisk, MassStorage,
MassStorageData, NibbleDisk, NibbleFormat, NoFloppyDisk, NO_DISK, PROCESS_BINARY, PROCESS_JSON, PROCESS_JSON_DISK, SupportedSectors, WozDisk
MassStorageData, NibbleDisk, NibbleFormat, NO_DISK, PROCESS_BINARY, PROCESS_JSON, PROCESS_JSON_DISK, SupportedSectors, WozDisk
} from '../formats/types';
import {
@ -19,11 +18,16 @@ import {
} from '../formats/create_disk';
import { jsonDecode, jsonEncode, readSector, _D13O, _DO, _PO } from '../formats/format_utils';
import { toHex } from '../util';
import Apple2IO from '../apple2io';
import { BOOTSTRAP_ROM_13, BOOTSTRAP_ROM_16 } from '../roms/cards/disk2';
import { EmptyDriver } from './drivers/EmptyDriver';
import { NibbleDiskDriver } from './drivers/NibbleDiskDriver';
import { ControllerState, DiskDriver, Drive, DriverState, Phase } from './drivers/types';
import { WozDiskDriver } from './drivers/WozDiskDriver';
/** Softswitch locations */
const LOC = {
// Disk II Controller Commands
@ -111,7 +115,7 @@ const SEQUENCER_ROM_16 = [
] as const;
/** Contents of the P6 sequencer ROM. */
const SEQUENCER_ROM: Record<SupportedSectors, ReadonlyArray<byte>> = {
export const SEQUENCER_ROM: Record<SupportedSectors, ReadonlyArray<byte>> = {
13: SEQUENCER_ROM_13,
16: SEQUENCER_ROM_16,
} as const;
@ -122,10 +126,6 @@ const BOOTSTRAP_ROM: Record<SupportedSectors, ReadonlyUint8Array> = {
16: BOOTSTRAP_ROM_16,
} as const;
type LssClockCycle = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7;
type LssState = nibble;
type Phase = 0 | 1 | 2 | 3;
/**
* How far the head moves, in quarter tracks, when in phase X and phase Y is
* activated. For example, if in phase 0 (top row), turning on phase 3 would
@ -155,49 +155,6 @@ const PHASE_DELTA = [
[1, -2, -1, 0]
] as const;
/**
* State of the controller.
*/
interface ControllerState {
/** Sectors supported by the controller. */
sectors: SupportedSectors;
/** Is the active drive powered on? */
on: boolean;
/** The active drive. */
driveNo: DriveNumber;
/** The 8-cycle LSS clock. */
clock: LssClockCycle;
/** Current state of the Logic State Sequencer. */
state: nibble;
/** Q6 (Shift/Load) */
q6: boolean;
/** Q7 (Read/Write) */
q7: boolean;
/** Last data from the disk drive. */
latch: byte;
/** Last data written by the CPU to card softswitch 0x8D. */
bus: byte;
}
/** Interface for drivers for various disk types. */
interface DiskDriver {
tick(): void;
onQ6Low(): void;
onQ6High(readMode: boolean): void;
onDriveOn(): void;
onDriveOff(): void;
clampTrack(): void;
getState(): DriverState;
setState(state: DriverState): void;
}
type DriverState = EmptyDriverState | NibbleDiskDriverState | WozDiskDriverState;
/** Callbacks triggered by events of the drive or controller. */
export interface Callbacks {
/** Called when a drive turns on or off. */
@ -212,20 +169,6 @@ export interface Callbacks {
label: (driveNo: DriveNumber, name?: string, side?: string) => void;
}
/** Common information for Nibble and WOZ disks. */
interface Drive {
/** Whether the drive write protect is on. */
readOnly: boolean;
/** Quarter track position of read/write head. */
track: byte;
/** Position of the head on the track. */
head: byte;
/** Current active coil in the head stepper motor. */
phase: Phase;
/** Whether the drive has been written to since it was loaded. */
dirty: boolean;
}
interface DriveState {
disk: FloppyDisk;
driver: DriverState;
@ -237,17 +180,11 @@ interface DriveState {
}
/** State of the controller for saving/restoring. */
// TODO(flan): It's unclear whether reusing ControllerState here is a good idea.
interface State {
drives: DriveState[];
driver: DriverState[];
controllerState: ControllerState;
}
function getDiskState(disk: NoFloppyDisk): NoFloppyDisk;
function getDiskState(disk: NibbleDisk): NibbleDisk;
function getDiskState(disk: WozDisk): WozDisk;
function getDiskState(disk: FloppyDisk): FloppyDisk;
function getDiskState(disk: FloppyDisk): FloppyDisk {
if (isNoFloppyDisk(disk)) {
const { encoding, metadata, readOnly } = disk;
@ -294,429 +231,6 @@ function getDiskState(disk: FloppyDisk): FloppyDisk {
throw new Error('Unknown drive state');
}
interface EmptyDriverState { }
class EmptyDriver implements DiskDriver {
constructor(private readonly drive: Drive) { }
tick(): void {
// do nothing
}
onQ6Low(): void {
// do nothing
}
onQ6High(_readMode: boolean): void {
// do nothing
}
onDriveOn(): void {
// do nothing
}
onDriveOff(): void {
// do nothing
}
clampTrack(): void {
// For empty drives, the emulator clamps the track to 0 to 34,
// but real Disk II drives can seek past track 34 by at least a
// half track, usually a full track. Some 3rd party drives can
// seek to track 39.
if (this.drive.track < 0) {
this.drive.track = 0;
}
if (this.drive.track > 34) {
this.drive.track = 34;
}
}
getState() {
return {};
}
setState(_state: EmptyDriverState): void {
// do nothing
}
}
abstract class BaseDiskDriver implements DiskDriver {
constructor(
protected readonly driveNo: DriveNumber,
protected readonly drive: Drive,
protected readonly disk: NibbleDisk | WozDisk,
protected readonly controller: ControllerState) { }
/** Called frequently to ensure the disk is spinning. */
abstract tick(): void;
/** Called when Q6 is set LOW. */
abstract onQ6Low(): void;
/** Called when Q6 is set HIGH. */
abstract onQ6High(readMode: boolean): void;
/**
* Called when drive is turned on. This is guaranteed to be called
* only when the associated drive is toggled from off to on. This
* is also guaranteed to be called when a new disk is inserted when
* the drive is already on.
*/
abstract onDriveOn(): void;
/**
* Called when drive is turned off. This is guaranteed to be called
* only when the associated drive is toggled from on to off.
*/
abstract onDriveOff(): void;
debug(..._args: unknown[]) {
// debug(...args);
}
/**
* Called every time the head moves to clamp the track to a valid
* range.
*/
abstract clampTrack(): void;
isOn(): boolean {
return this.controller.on && this.controller.driveNo === this.driveNo;
}
isWriteProtected(): boolean {
return this.drive.readOnly;
}
abstract getState(): DriverState;
abstract setState(state: DriverState): void;
}
interface NibbleDiskDriverState {
skip: number;
nibbleCount: number;
}
class NibbleDiskDriver extends BaseDiskDriver {
/**
* When `1`, the next nibble will be available for read; when `0`,
* the card is pretending to wait for data to be shifted in by the
* sequencer.
*/
private skip: number = 0;
/** Number of nibbles reads since the drive was turned on. */
private nibbleCount: number = 0;
constructor(
driveNo: DriveNumber,
drive: Drive,
readonly disk: NibbleDisk,
controller: ControllerState,
private readonly onDirty: () => void) {
super(driveNo, drive, disk, controller);
}
tick(): void {
// do nothing
}
onQ6Low(): void {
const drive = this.drive;
const disk = this.disk;
if (this.isOn() && (this.skip || this.controller.q7)) {
const track = disk.tracks[drive.track >> 2];
if (track && track.length) {
if (drive.head >= track.length) {
drive.head = 0;
}
if (this.controller.q7) {
const writeProtected = disk.readOnly;
if (!writeProtected) {
track[drive.head] = this.controller.bus;
drive.dirty = true;
this.onDirty();
}
} else {
this.controller.latch = track[drive.head];
this.nibbleCount++;
}
++drive.head;
}
} else {
this.controller.latch = 0;
}
this.skip = (++this.skip % 2);
}
onQ6High(readMode: boolean): void {
const drive = this.drive;
if (readMode && !this.controller.q7) {
const writeProtected = drive.readOnly;
if (writeProtected) {
this.controller.latch = 0xff;
this.debug('Setting readOnly');
} else {
this.controller.latch >>= 1;
this.debug('Clearing readOnly');
}
}
}
onDriveOn(): void {
this.nibbleCount = 0;
}
onDriveOff(): void {
this.debug('nibbles read', this.nibbleCount);
}
clampTrack(): void {
// For NibbleDisks, the emulator clamps the track to the available
// range.
if (this.drive.track < 0) {
this.drive.track = 0;
}
const lastTrack = 35 * 4 - 1;
if (this.drive.track > lastTrack) {
this.drive.track = lastTrack;
}
}
getState(): NibbleDiskDriverState {
const { skip, nibbleCount } = this;
return { skip, nibbleCount };
}
setState(state: NibbleDiskDriverState) {
this.skip = state.skip;
this.nibbleCount = state.nibbleCount;
}
}
interface WozDiskDriverState {
clock: LssClockCycle;
state: LssState;
lastCycles: number;
zeros: number;
}
class WozDiskDriver extends BaseDiskDriver {
/** Logic state sequencer clock cycle. */
private clock: LssClockCycle;
/** Logic state sequencer state. */
private state: LssState;
/** Current CPU cycle count. */
private lastCycles: number = 0;
/**
* Number of zeros read in a row. The Disk ][ can only read two zeros in a
* row reliably; above that and the drive starts reporting garbage. See
* "Freaking Out Like a MC3470" in the WOZ spec.
*/
private zeros = 0;
constructor(
driveNo: DriveNumber,
drive: Drive,
readonly disk: WozDisk,
controller: ControllerState,
private readonly onDirty: () => void,
private readonly io: Apple2IO) {
super(driveNo, drive, disk, controller);
// From the example in UtA2e, p. 9-29, col. 1, para. 1., this is
// essentially the start of the sequencer loop and produces
// correctly synced nibbles immediately. Starting at state 0
// would introduce a spurrious 1 in the latch at the beginning,
// which requires reading several more sync bytes to sync up.
this.state = 2;
this.clock = 0;
}
onDriveOn(): void {
this.lastCycles = this.io.cycles();
}
onDriveOff(): void {
// nothing
}
/**
* Spin the disk under the read/write head for WOZ images.
*
* This implementation emulates every clock cycle of the 2 MHz
* sequencer since the last time it was called in order to
* determine the current state. Because this is called on
* every access to the softswitches, the data in the latch
* will be correct on every read.
*
* The emulation of the disk makes a few simplifying assumptions:
*
* * The motor turns on instantly.
* * The head moves tracks instantly.
* * The length (in bits) of each track of the WOZ image
* represents one full rotation of the disk and that each
* bit is evenly spaced.
* * Writing will not change the track length. This means
* that short tracks stay short.
* * The read head picks up the next bit when the sequencer
* clock === 4.
* * Head position X on track T is equivalent to head position
* X on track T′. (This is not the recommendation in the WOZ
* spec.)
* * Unspecified tracks contain a single zero bit. (A very
* short track, indeed!)
* * Two zero bits are sufficient to cause the MC3470 to freak
* out. When freaking out, it returns 0 and 1 with equal
* probability.
* * Any softswitch changes happen before `moveHead`. This is
* important because it means that if the clock is ever
* advanced more than one cycle between calls, the
* softswitch changes will appear to happen at the very
* beginning, not just before the last cycle.
*/
private moveHead() {
// TODO(flan): Short-circuit if the drive is not on.
const cycles = this.io.cycles();
// Spin the disk the number of elapsed cycles since last call
let workCycles = (cycles - this.lastCycles) * 2;
this.lastCycles = cycles;
const drive = this.drive;
const disk = this.disk;
const controller = this.controller;
// TODO(flan): Improve unformatted track behavior. The WOZ
// documentation suggests using an empty track of 6400 bytes
// (51,200 bits).
const track =
disk.rawTracks[disk.trackMap[drive.track]] || [0];
while (workCycles-- > 0) {
let pulse: number = 0;
if (this.clock === 4) {
pulse = track[drive.head];
if (!pulse) {
// More than 2 zeros can not be read reliably.
// TODO(flan): Revisit with the new MC3470
// suggested 4-bit window behavior.
if (++this.zeros > 2) {
const r = Math.random();
pulse = r >= 0.5 ? 1 : 0;
}
} else {
this.zeros = 0;
}
}
let idx = 0;
idx |= pulse ? 0x00 : 0x01;
idx |= controller.latch & 0x80 ? 0x02 : 0x00;
idx |= controller.q6 ? 0x04 : 0x00;
idx |= controller.q7 ? 0x08 : 0x00;
idx |= this.state << 4;
const command = SEQUENCER_ROM[controller.sectors][idx];
this.debug(`clock: ${this.clock} state: ${toHex(this.state)} pulse: ${pulse} command: ${toHex(command)} q6: ${controller.q6} latch: ${toHex(controller.latch)}`);
switch (command & 0xf) {
case 0x0: // CLR
controller.latch = 0;
break;
case 0x8: // NOP
break;
case 0x9: // SL0
controller.latch = (controller.latch << 1) & 0xff;
break;
case 0xA: // SR
controller.latch >>= 1;
if (this.isWriteProtected()) {
controller.latch |= 0x80;
}
break;
case 0xB: // LD
controller.latch = controller.bus;
this.debug('Loading', toHex(controller.latch), 'from bus');
break;
case 0xD: // SL1
controller.latch = ((controller.latch << 1) | 0x01) & 0xff;
break;
default:
this.debug(`unknown command: ${toHex(command & 0xf)}`);
}
this.state = (command >> 4 & 0xF) as LssState;
if (this.clock === 4) {
if (this.isOn()) {
if (controller.q7) {
// TODO(flan): This assumes that writes are happening in
// a "friendly" way, namely where the track was originally
// written. To do this correctly, the virtual head should
// actually keep track of the current quarter track plus
// the one on each side. Then, when writing, it should
// check that all three are actually the same rawTrack. If
// they aren't, then the trackMap has to be updated as
// well.
track[drive.head] = this.state & 0x8 ? 0x01 : 0x00;
this.debug('Wrote', this.state & 0x8 ? 0x01 : 0x00);
drive.dirty = true;
this.onDirty();
}
if (++drive.head >= track.length) {
drive.head = 0;
}
}
}
if (++this.clock > 7) {
this.clock = 0;
}
}
}
tick(): void {
this.moveHead();
}
onQ6High(_readMode: boolean): void {
// nothing?
}
onQ6Low(): void {
// nothing?
}
clampTrack(): void {
// For NibbleDisks, the emulator clamps the track to the available
// range.
if (this.drive.track < 0) {
this.drive.track = 0;
}
const lastTrack = this.disk.trackMap.length - 1;
if (this.drive.track > lastTrack) {
this.drive.track = lastTrack;
}
}
getState(): WozDiskDriverState {
const { clock, state, lastCycles, zeros } = this;
return { clock, state, lastCycles, zeros };
}
setState(state: WozDiskDriverState) {
this.clock = state.clock;
this.state = state.state;
this.lastCycles = state.lastCycles;
this.zeros = state.zeros;
}
}
/**
* Emulates the 16-sector and 13-sector versions of the Disk ][ drive and controller.
*/
@ -1015,7 +529,6 @@ export default class DiskII implements Card<State>, MassStorage<NibbleFormat> {
getState(): State {
const result = {
drives: [] as DriveState[],
driver: [] as DriverState[],
controllerState: { ...this.state },
};
result.drives[1] = this.getDriveState(1);

63
js/cards/drivers/BaseDiskDriver.ts Normal file
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@ -0,0 +1,63 @@
import { DriveNumber, NibbleDisk, WozDisk } from '../../formats/types';
import { ControllerState, DiskDriver, Drive, DriverState } from './types';
/**
* Common logic for both `NibbleDiskDriver` and `WozDiskDriver`.
*/
export abstract class BaseDiskDriver implements DiskDriver {
constructor(
protected readonly driveNo: DriveNumber,
protected readonly drive: Drive,
protected readonly disk: NibbleDisk | WozDisk,
protected readonly controller: ControllerState) { }
/** Called frequently to ensure the disk is spinning. */
abstract tick(): void;
/** Called when Q6 is set LOW. */
abstract onQ6Low(): void;
/** Called when Q6 is set HIGH. */
abstract onQ6High(readMode: boolean): void;
/**
* Called when drive is turned on. This is guaranteed to be called
* only when the associated drive is toggled from off to on. This
* is also guaranteed to be called when a new disk is inserted when
* the drive is already on.
*/
abstract onDriveOn(): void;
/**
* Called when drive is turned off. This is guaranteed to be called
* only when the associated drive is toggled from on to off.
*/
abstract onDriveOff(): void;
debug(..._args: unknown[]) {
// debug(...args);
}
/**
* Called every time the head moves to clamp the track to a valid
* range.
*/
abstract clampTrack(): void;
/** Returns `true` if the controller is on and this drive is selected. */
isOn(): boolean {
return this.controller.on && this.controller.driveNo === this.driveNo;
}
/** Returns `true` if the drive's write protect switch is enabled. */
isWriteProtected(): boolean {
return this.drive.readOnly;
}
/** Returns the current state of the driver as a serializable object. */
abstract getState(): DriverState;
/** Sets the state of the driver from the given `state`. */
abstract setState(state: DriverState): void;
}

53
js/cards/drivers/EmptyDriver.ts Normal file
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@ -0,0 +1,53 @@
import { DiskDriver, Drive, DriverState } from './types';
/** Returned state for an empty drive. */
export interface EmptyDriverState extends DriverState { }
/**
* Driver for empty drives. This implementation does nothing except keep
* the head clamped between tracks 0 and 34.
*/
export class EmptyDriver implements DiskDriver {
constructor(private readonly drive: Drive) { }
tick(): void {
// do nothing
}
onQ6Low(): void {
// do nothing
}
onQ6High(_readMode: boolean): void {
// do nothing
}
onDriveOn(): void {
// do nothing
}
onDriveOff(): void {
// do nothing
}
clampTrack(): void {
// For empty drives, the emulator clamps the track to 0 to 34,
// but real Disk II drives can seek past track 34 by at least a
// half track, usually a full track. Some 3rd party drives can
// seek to track 39.
if (this.drive.track < 0) {
this.drive.track = 0;
}
if (this.drive.track > 34) {
this.drive.track = 34;
}
}
getState() {
return {};
}
setState(_state: EmptyDriverState): void {
// do nothing
}
}

106
js/cards/drivers/NibbleDiskDriver.ts Normal file
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@ -0,0 +1,106 @@
import { DriveNumber, NibbleDisk } from '../../formats/types';
import { BaseDiskDriver } from './BaseDiskDriver';
import { ControllerState, Drive, DriverState } from './types';
interface NibbleDiskDriverState extends DriverState {
skip: number;
nibbleCount: number;
}
export class NibbleDiskDriver extends BaseDiskDriver {
/**
* When `1`, the next nibble will be available for read; when `0`,
* the card is pretending to wait for data to be shifted in by the
* sequencer.
*/
private skip: number = 0;
/** Number of nibbles reads since the drive was turned on. */
private nibbleCount: number = 0;
constructor(
driveNo: DriveNumber,
drive: Drive,
readonly disk: NibbleDisk,
controller: ControllerState,
private readonly onDirty: () => void) {
super(driveNo, drive, disk, controller);
}
tick(): void {
// do nothing
}
onQ6Low(): void {
const drive = this.drive;
const disk = this.disk;
if (this.isOn() && (this.skip || this.controller.q7)) {
const track = disk.tracks[drive.track >> 2];
if (track && track.length) {
if (drive.head >= track.length) {
drive.head = 0;
}
if (this.controller.q7) {
const writeProtected = disk.readOnly;
if (!writeProtected) {
track[drive.head] = this.controller.bus;
drive.dirty = true;
this.onDirty();
}
} else {
this.controller.latch = track[drive.head];
this.nibbleCount++;
}
++drive.head;
}
} else {
this.controller.latch = 0;
}
this.skip = (++this.skip % 2);
}
onQ6High(readMode: boolean): void {
const drive = this.drive;
if (readMode && !this.controller.q7) {
const writeProtected = drive.readOnly;
if (writeProtected) {
this.controller.latch = 0xff;
this.debug('Setting readOnly');
} else {
this.controller.latch >>= 1;
this.debug('Clearing readOnly');
}
}
}
onDriveOn(): void {
this.nibbleCount = 0;
}
onDriveOff(): void {
this.debug('nibbles read', this.nibbleCount);
}
clampTrack(): void {
// For NibbleDisks, the emulator clamps the track to the available
// range.
if (this.drive.track < 0) {
this.drive.track = 0;
}
const lastTrack = 35 * 4 - 1;
if (this.drive.track > lastTrack) {
this.drive.track = lastTrack;
}
}
getState(): NibbleDiskDriverState {
const { skip, nibbleCount } = this;
return { skip, nibbleCount };
}
setState(state: NibbleDiskDriverState) {
this.skip = state.skip;
this.nibbleCount = state.nibbleCount;
}
}

225
js/cards/drivers/WozDiskDriver.ts Normal file
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@ -0,0 +1,225 @@
import Apple2IO from '../../apple2io';
import { DriveNumber, WozDisk } from '../../formats/types';
import { toHex } from '../../util';
import { SEQUENCER_ROM } from '../disk2';
import { BaseDiskDriver } from './BaseDiskDriver';
import { ControllerState, Drive, DriverState, LssClockCycle, LssState } from './types';
interface WozDiskDriverState extends DriverState {
clock: LssClockCycle;
state: LssState;
lastCycles: number;
zeros: number;
}
export class WozDiskDriver extends BaseDiskDriver {
/** Logic state sequencer clock cycle. */
private clock: LssClockCycle;
/** Logic state sequencer state. */
private state: LssState;
/** Current CPU cycle count. */
private lastCycles: number = 0;
/**
* Number of zeros read in a row. The Disk ][ can only read two zeros in a
* row reliably; above that and the drive starts reporting garbage. See
* "Freaking Out Like a MC3470" in the WOZ spec.
*/
private zeros = 0;
constructor(
driveNo: DriveNumber,
drive: Drive,
readonly disk: WozDisk,
controller: ControllerState,
private readonly onDirty: () => void,
private readonly io: Apple2IO) {
super(driveNo, drive, disk, controller);
// From the example in UtA2e, p. 9-29, col. 1, para. 1., this is
// essentially the start of the sequencer loop and produces
// correctly synced nibbles immediately. Starting at state 0
// would introduce a spurrious 1 in the latch at the beginning,
// which requires reading several more sync bytes to sync up.
this.state = 2;
this.clock = 0;
}
onDriveOn(): void {
this.lastCycles = this.io.cycles();
}
onDriveOff(): void {
// nothing
}
/**
* Spin the disk under the read/write head for WOZ images.
*
* This implementation emulates every clock cycle of the 2 MHz
* sequencer since the last time it was called in order to
* determine the current state. Because this is called on
* every access to the softswitches, the data in the latch
* will be correct on every read.
*
* The emulation of the disk makes a few simplifying assumptions:
*
* * The motor turns on instantly.
* * The head moves tracks instantly.
* * The length (in bits) of each track of the WOZ image
* represents one full rotation of the disk and that each
* bit is evenly spaced.
* * Writing will not change the track length. This means
* that short tracks stay short.
* * The read head picks up the next bit when the sequencer
* clock === 4.
* * Head position X on track T is equivalent to head position
* X on track T′. (This is not the recommendation in the WOZ
* spec.)
* * Unspecified tracks contain a single zero bit. (A very
* short track, indeed!)
* * Two zero bits are sufficient to cause the MC3470 to freak
* out. When freaking out, it returns 0 and 1 with equal
* probability.
* * Any softswitch changes happen before `moveHead`. This is
* important because it means that if the clock is ever
* advanced more than one cycle between calls, the
* softswitch changes will appear to happen at the very
* beginning, not just before the last cycle.
*/
private moveHead() {
// TODO(flan): Short-circuit if the drive is not on.
const cycles = this.io.cycles();
// Spin the disk the number of elapsed cycles since last call
let workCycles = (cycles - this.lastCycles) * 2;
this.lastCycles = cycles;
const drive = this.drive;
const disk = this.disk;
const controller = this.controller;
// TODO(flan): Improve unformatted track behavior. The WOZ
// documentation suggests using an empty track of 6400 bytes
// (51,200 bits).
const track = disk.rawTracks[disk.trackMap[drive.track]] || [0];
while (workCycles-- > 0) {
let pulse: number = 0;
if (this.clock === 4) {
pulse = track[drive.head];
if (!pulse) {
// More than 2 zeros can not be read reliably.
// TODO(flan): Revisit with the new MC3470
// suggested 4-bit window behavior.
if (++this.zeros > 2) {
const r = Math.random();
pulse = r >= 0.5 ? 1 : 0;
}
} else {
this.zeros = 0;
}
}
let idx = 0;
idx |= pulse ? 0x00 : 0x01;
idx |= controller.latch & 0x80 ? 0x02 : 0x00;
idx |= controller.q6 ? 0x04 : 0x00;
idx |= controller.q7 ? 0x08 : 0x00;
idx |= this.state << 4;
const command = SEQUENCER_ROM[controller.sectors][idx];
this.debug(`clock: ${this.clock} state: ${toHex(this.state)} pulse: ${pulse} command: ${toHex(command)} q6: ${controller.q6} latch: ${toHex(controller.latch)}`);
switch (command & 0xf) {
case 0x0: // CLR
controller.latch = 0;
break;
case 0x8: // NOP
break;
case 0x9: // SL0
controller.latch = (controller.latch << 1) & 0xff;
break;
case 0xA: // SR
controller.latch >>= 1;
if (this.isWriteProtected()) {
controller.latch |= 0x80;
}
break;
case 0xB: // LD
controller.latch = controller.bus;
this.debug('Loading', toHex(controller.latch), 'from bus');
break;
case 0xD: // SL1
controller.latch = ((controller.latch << 1) | 0x01) & 0xff;
break;
default:
this.debug(`unknown command: ${toHex(command & 0xf)}`);
}
this.state = (command >> 4 & 0xF) as LssState;
if (this.clock === 4) {
if (this.isOn()) {
if (controller.q7) {
// TODO(flan): This assumes that writes are happening in
// a "friendly" way, namely where the track was originally
// written. To do this correctly, the virtual head should
// actually keep track of the current quarter track plus
// the one on each side. Then, when writing, it should
// check that all three are actually the same rawTrack. If
// they aren't, then the trackMap has to be updated as
// well.
track[drive.head] = this.state & 0x8 ? 0x01 : 0x00;
this.debug('Wrote', this.state & 0x8 ? 0x01 : 0x00);
drive.dirty = true;
this.onDirty();
}
if (++drive.head >= track.length) {
drive.head = 0;
}
}
}
if (++this.clock > 7) {
this.clock = 0;
}
}
}
tick(): void {
this.moveHead();
}
onQ6High(_readMode: boolean): void {
// nothing?
}
onQ6Low(): void {
// nothing?
}
clampTrack(): void {
// For NibbleDisks, the emulator clamps the track to the available
// range.
if (this.drive.track < 0) {
this.drive.track = 0;
}
const lastTrack = this.disk.trackMap.length - 1;
if (this.drive.track > lastTrack) {
this.drive.track = lastTrack;
}
}
getState(): WozDiskDriverState {
const { clock, state, lastCycles, zeros } = this;
return { clock, state, lastCycles, zeros };
}
setState(state: WozDiskDriverState) {
this.clock = state.clock;
this.state = state.state;
this.lastCycles = state.lastCycles;
this.zeros = state.zeros;
}
}

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import { DriveNumber, SupportedSectors } from 'js/formats/types';
import { byte, nibble } from 'js/types';
export type LssClockCycle = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7;
export type LssState = nibble;
export type Phase = 0 | 1 | 2 | 3;
/**
* State of the controller.
*/
export interface ControllerState {
/** Sectors supported by the controller. */
sectors: SupportedSectors;
/** Is the active drive powered on? */
on: boolean;
/** The active drive. */
driveNo: DriveNumber;
/** The 8-cycle LSS clock. */
clock: LssClockCycle;
/** Current state of the Logic State Sequencer. */
state: LssState;
/** Q6 (Shift/Load) */
q6: boolean;
/** Q7 (Read/Write) */
q7: boolean;
/** Last data from the disk drive. */
latch: byte;
/** Last data written by the CPU to card softswitch 0x8D. */
bus: byte;
}
/** Common information for Nibble and WOZ disks. */
export interface Drive {
/** Whether the drive write protect is on. */
readOnly: boolean;
/** Quarter track position of read/write head. */
track: byte;
/** Position of the head on the track. */
head: byte;
/** Current active coil in the head stepper motor. */
phase: Phase;
/** Whether the drive has been written to since it was loaded. */
dirty: boolean;
}
/** Base interface for disk driver states. */
export interface DriverState {}
/** Interface for drivers for various disk types. */
export interface DiskDriver {
tick(): void;
onQ6Low(): void;
onQ6High(readMode: boolean): void;
onDriveOn(): void;
onDriveOff(): void;
clampTrack(): void;
getState(): DriverState;
setState(state: DriverState): void;
}