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