Press n or j to go to the next uncovered block, b, p or k for the previous block.
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975x 975x 6824x 284x 283x 283x 6929x 20x 1480x 25x 25x 25x 25x 25x 25x 129x 129x 25x 25x 104x 38194x 34672x 34672x 234806x 32042x 4967x 4967x 2399x 2398x 2399x 2399x 2399x 891x 2399x 2399x 2399x 2399x 6325x 6325x 6325x 6325x 153x 153x 4x 4x 298x 298x 298x 298x 382x 191x 3x 922x 922x 922x 35x 35x | import { BBC, getKeyMap, WithKeyMatrix } from "./keymap.js";
const ORB = 0x0,
ORA = 0x1,
DDRB = 0x2,
DDRA = 0x3,
T1CL = 0x4,
T1CH = 0x5,
T1LL = 0x6,
T1LH = 0x7,
T2CL = 0x8,
T2CH = 0x9,
SR = 0xa,
ACR = 0xb,
PCR = 0xc,
IFR = 0xd,
IER = 0xe,
ORAnh = 0xf,
TIMER1INT = 0x40,
TIMER2INT = 0x20,
INT_CA1 = 0x02,
INT_CA2 = 0x01,
INT_CB1 = 0x10,
INT_CB2 = 0x08,
INT_SR = 0x04;
// The shift register's modes, ACR bits 2 to 4. Bit 2 of the mode is set for the shifts out, and modes 3 and 7 take
// their clock from CB1.
const ShiftDisabled = 0,
ShiftInT2 = 1,
ShiftOutFreeRunningT2 = 4,
ShiftOutT2 = 5,
ShiftOut = 4,
AcrShiftModeShift = 2,
AcrShiftMode = 0x1c,
AcrShiftExternal = 0x0c;
const T2ClockedShiftModes = (1 << ShiftInT2) | (1 << ShiftOutFreeRunningT2) | (1 << ShiftOutT2);
const BitsPerShift = 8;
const TicksPerViaCycle = 2;
// The first edge of a φ2-clocked shift comes two cycles after the SR access, and a shift in sets its flag a cycle
// after its last rising edge. Both from MAME's 6522via.cpp, as beebjit models only the free-running mode.
const Phi2FirstEdgeTicks = 2 * TicksPerViaCycle;
const ShiftInFlagDelayTicks = TicksPerViaCycle;
// Pulse mode holds CA2/CB2 low for one 1MHz VIA cycle, here in the scheduler's 2MHz ticks.
// Figures 3-4 and 3-6 of https://6502.org/documents/datasheets/wdc/wdc_w65c22s_mar_2004.pdf
const PulseWidthCycles = 2;
// Reset makes every pin an input, and undriven inputs float high.
const IdlePins = 0xff;
// The autoscan counter steps through 16 columns, one per 1MHz cycle (two 2MHz scheduler ticks), of which the keyboard
// wires 10 on a B and 13 on a Master.
const ScanCounterColumns = 16;
const TicksPerScanColumn = 2;
const KeyboardColumns = 13;
// The joystick FIRE buttons pull PB4 and PB5 low (AUG p418).
const JoystickFire1 = 1 << 4;
const JoystickFire2 = 1 << 5;
class Via {
constructor(cpu, scheduler, irq) {
this.cpu = cpu;
this.irq = irq;
this.scheduler = scheduler;
this.ora = 0;
this.orb = 0;
this.ira = 0;
this.irb = 0;
this.ddra = 0;
this.ddrb = 0;
this.sr = 0;
this.t1l = 0;
this.t2l = 0;
this.t1c = 0;
this.t2c = 0;
this.acr = 0;
this.pcr = 0;
this.ifr = 0;
this.ier = 0;
this.t1hit = false;
this.t2hit = false;
this.t2High = 0;
this.portapins = IdlePins;
this.portbpins = IdlePins;
this.ca1 = false;
this.ca2 = false;
this.cb1 = false;
this.cb2 = false;
this.ca2changecallback = null;
this.cb2changecallback = null;
this.justhit = 0;
this.t1_pb7 = 0;
this.shiftBits = BitsPerShift;
this.task = this.scheduler.newTask(() => this._onTimeout());
this.shiftTask = this.scheduler.newTask(() => this._onShiftEdge());
this.ca2PulseTask = this.scheduler.newTask(() => this.setca2(true));
this.cb2PulseTask = this.scheduler.newTask(() => this.setcb2(true));
this.lastPolltime = 0;
}
reset() {
// http://archive.6502.org/datasheets/mos_6522_preliminary_nov_1977.pdf
// "Reset sets all registers to zero except t1 t2 and sr"
this.ora = this.orb = 0x00;
this.ddra = this.ddrb = 0x00;
this.ifr = this.ier = 0x00;
this.t1c = this.t1l = this.t2c = this.t2l = 0x1fffe;
this.t1hit = this.t2hit = true;
this.acr = this.pcr = 0;
this.t2High = 0;
this.t1_pb7 = 1;
this.portapins = this.portbpins = IdlePins;
this.ca2PulseTask.cancel();
this.cb2PulseTask.cancel();
this._stopShiftClockAtRest();
this.shiftBits = BitsPerShift;
this.updateNextTime();
}
_shiftMode() {
return (this.acr & AcrShiftMode) >>> AcrShiftModeShift;
}
_t2ClocksShifter() {
return !!((T2ClockedShiftModes >>> this._shiftMode()) & 1);
}
_t2CountsPulses() {
return !!(this.acr & 0x20) && !this._t2ClocksShifter();
}
_t2ShiftPeriod() {
return (this.t2l & 0x1fe) + 4;
}
_splitT2ForShifting() {
const count = this.t2c + 1;
this.t2High = (count >>> 9) & 0xff;
this.t2c = (count & 0x1ff) - 1;
}
// Between an underflow and its relatch, t2High has already stepped down for it.
_joinT2FromShifting() {
this.t2c += (this.t2High + (this.t2c < -2 ? 1 : 0)) << 9;
}
updateNextTime() {
let nextTimer = this.t1c;
if (this._t2ClocksShifter()) {
if (!this.t2hit) {
const underflowsToWrap = this.t2High + (this.t2c < -2 ? 1 : 0);
nextTimer = Math.min(this.t2c + underflowsToWrap * this._t2ShiftPeriod(), nextTimer);
}
} else if (!(this.acr & 0x20)) nextTimer = Math.min(this.t2c, nextTimer);
this.task.reschedule(Math.max(1, nextTimer));
}
_onTimeout() {
this._catchUp();
}
_catchUp() {
const cycles = this.scheduler.epoch - this.lastPolltime;
if (cycles) this._polltime(cycles);
this.lastPolltime = this.scheduler.epoch;
this.updateNextTime();
}
_polltime(cycles) {
cycles |= 0;
this.justhit = 0;
const newT1c = this.t1c - cycles;
if (newT1c < -2) this.t1c = this._handleT1c(newT1c);
else this.t1c = newT1c;
if (this._t2ClocksShifter()) {
this._pollT2Shifting(cycles);
} else if (!(this.acr & 0x20)) {
const newT2c = this.t2c - cycles;
if (newT2c < -2) this.t2c = this._handleT2c(newT2c);
else this.t2c = newT2c;
}
}
_handleT1c(newT1c) {
if (newT1c < -2 && this.t1c > -3) {
if (!this.t1hit) {
this.ifr |= TIMER1INT;
this.updateIFR();
Eif (newT1c === -3) this.justhit |= 1;
this.t1_pb7 = !this.t1_pb7;
}
if (!(this.acr & 0x40)) this.t1hit = true;
}
while (newT1c < -3) newT1c += this.t1l + 4;
return newT1c;
}
// T2 high steps down as T2 low reaches FF (-3, as in 16-bit mode), and the relatch lands a cycle later. See
// beebjit via.c via_shift_fired and make_timing_rom.c.
_pollT2Shifting(cycles) {
const period = this._t2ShiftPeriod();
let newT2c = this.t2c - cycles;
if (newT2c <= -3) {
const firstUnderflow = this.t2c > -3 ? 0 : 1;
const lastUnderflow = Math.floor((-3 - newT2c) / period);
const underflows = lastUnderflow - firstUnderflow + 1;
if (underflows > this.t2High && !this.t2hit) {
this.ifr |= TIMER2INT;
this.updateIFR();
Eif (newT2c === -3 - (firstUnderflow + this.t2High) * period) this.justhit |= 2;
this.t2hit = true;
}
this.t2High = (this.t2High - underflows) & 0xff;
}
if (newT2c < -4) newT2c += Math.ceil((-4 - newT2c) / period) * period;
this.t2c = newT2c;
}
_handleT2c(newT2c) {
if (!this.t2hit) {
this.ifr |= TIMER2INT;
this.updateIFR();
Eif (newT2c === -3) this.justhit |= 2;
this.t2hit = true;
}
newT2c += 0x20000;
return newT2c;
}
/**
* Reading or writing SR clears its flag, restarts an external clock's count of eight, and starts an internally
* clocked shift unless one is under way. A write to one under way restarts its count without moving its clock,
* and a read leaves it alone, as MAME's 6522via.cpp has it. The free-running mode, once started, runs until the
* mode changes.
*/
_accessShiftRegister(isWrite) {
this.ifr &= ~INT_SR;
this.updateIFR();
const mode = this._shiftMode();
if ((this.acr & AcrShiftExternal) === AcrShiftExternal) {
this.shiftBits = BitsPerShift;
return;
}
if (mode === ShiftDisabled) return;
if (this._shiftUnderWay()) {
if (isWrite) this.shiftBits = BitsPerShift;
return;
}
this.shiftBits = BitsPerShift;
// CB1 is the shift clock's output, which rests high.
this.cb1 = true;
this.shiftTask.reschedule(this._t2ClocksShifter() ? this._ticksToT2Underflow() : Phi2FirstEdgeTicks);
}
_stopShiftClockAtRest() {
if (this.shiftTask.scheduled()) this.cb1 = true;
this.shiftTask.cancel();
}
// Once a shift in's last bit is in, its task waits only to set the flag.
_shiftUnderWay() {
return this.shiftTask.scheduled() && !(this.shiftBits === 0 && this.cb1);
}
_ticksToT2Underflow() {
return this.t2c + 3 + (this.t2c > -3 ? 0 : this._t2ShiftPeriod());
}
/**
* An edge of an internal shift clock: T2's low byte reaching FF, as beebjit's via_shift_fired, or each φ2 cycle.
* Bits go out on CB2 on the falling edge and come in from CB2 on the rising one, as in the 6522 datasheets.
*/
_onShiftEdge() {
this._catchUp();
if (!this.shiftBits && this.cb1) {
this._raiseShiftFlag();
return;
}
const rising = !this.cb1;
this.cb1 = rising;
const mode = this._shiftMode();
if (mode & ShiftOut) {
if (!rising) {
this._shiftOut();
--this.shiftBits;
} else if (!this.shiftBits) {
if (mode !== ShiftOutFreeRunningT2) {
this._raiseShiftFlag();
return;
}
this.shiftBits = BitsPerShift;
}
} else if (rising) {
this._shiftIn();
if (!--this.shiftBits) {
this.shiftTask.schedule(ShiftInFlagDelayTicks);
return;
}
}
this.shiftTask.schedule(this._t2ClocksShifter() ? this._ticksToT2Underflow() : TicksPerViaCycle);
}
/** Modes 3 and 7: an external clock on CB1 shifts in on its rising edges and out on its falling ones. */
_clockShiftFromCb1(rising) {
if (this.acr & (ShiftOut << AcrShiftModeShift)) {
if (rising) return;
this._shiftOut();
} else {
if (!rising) return;
this._shiftIn();
}
if (!--this.shiftBits) {
this.shiftBits = BitsPerShift;
this._raiseShiftFlag();
}
}
_shiftOut() {
const bit = this.sr >>> 7;
this.sr = ((this.sr << 1) | bit) & 0xff;
const level = !!bit;
if (level === this.cb2) return;
this.cb2 = level;
if (this.cb2changecallback) this.cb2changecallback(level, true);
}
_shiftIn() {
this.sr = ((this.sr << 1) | (this.cb2 ? 1 : 0)) & 0xff;
}
_raiseShiftFlag() {
this.ifr |= INT_SR;
this.updateIFR();
}
updateIFR() {
if (this.ifr & this.ier & 0x7f) {
this.ifr |= 0x80;
this.cpu.interrupt |= this.irq;
} else {
this.ifr &= ~0x80;
this.cpu.interrupt &= ~this.irq;
}
}
write(addr, val) {
this._catchUp();
let mode;
val |= 0;
switch (addr & 0xf) {
case ORA:
this.ifr &= ~INT_CA1;
Eif ((this.pcr & 0x0a) !== 0x02) {
// b-em: Not independent interrupt for CA2
this.ifr &= ~INT_CA2;
}
this.updateIFR();
// The strobe is "data ready": the port settles before CA2 falls.
// http://archive.6502.org/datasheets/wdc_w65c22s_mar_2004.pdf figures 3-6 and 3-7.
this.ora = val;
this.recalculatePortAPins();
mode = this.pcr & 0x0e;
if (mode === 8) {
// Handshake mode
this.setca2(false);
} else if (mode === 0x0a) {
// Pulse mode
this.setca2(false);
this.ca2PulseTask.reschedule(PulseWidthCycles);
}
break;
case ORAnh:
this.ora = val;
this.recalculatePortAPins();
break;
case ORB:
this.ifr &= ~INT_CB1;
Eif ((this.pcr & 0xa0) !== 0x20) {
// b-em: Not independent interrupt for CB2
this.ifr &= ~INT_CB2;
}
this.updateIFR();
this.orb = val;
this.recalculatePortBPins();
mode = (this.pcr & 0xe0) >>> 4;
if (mode === 8) {
// Handshake mode
this.setcb2(false);
} else if (mode === 0x0a) {
// Pulse mode
this.setcb2(false);
this.cb2PulseTask.reschedule(PulseWidthCycles);
}
break;
case DDRA:
this.ddra = val;
this.recalculatePortAPins();
break;
case DDRB:
this.ddrb = val;
this.recalculatePortBPins();
break;
case ACR: {
const wasShifting = this._t2ClocksShifter();
const wasCountingPulses = this._t2CountsPulses();
if ((this.acr ^ val) & AcrShiftMode) {
this._stopShiftClockAtRest();
this.shiftBits = BitsPerShift;
}
this.acr = val;
Iif (this.justhit & 1 && !(val & 0x40)) this.t1hit = true;
const isShifting = this._t2ClocksShifter();
if (!wasShifting && isShifting) this._splitT2ForShifting();
else if (wasShifting && !isShifting) this._joinT2FromShifting();
// T2 ticks once more before freezing, and resumes a tick late. See beebjit via.c via_write_ACR.
if (!isShifting) {
const isCountingPulses = this._t2CountsPulses();
if (!wasCountingPulses && isCountingPulses) {
this.t2c -= 2;
if (this.t2c < -2) this.t2c = this._handleT2c(this.t2c);
} else if (wasCountingPulses && !isCountingPulses) {
this.t2c += 2;
}
}
this.updateNextTime();
break;
}
case PCR:
this.pcr = val;
if ((val & 0xe) === 0xc) this.setca2(false);
else if (val & 0x08) this.setca2(true);
Iif ((val & 0xe0) === 0xc0) this.setcb2(false);
else if (val & 0x80) this.setcb2(true);
break;
case SR:
this.sr = val;
this._accessShiftRegister(true);
break;
case T1LL:
case T1CL:
this.t1l &= 0x1fe00;
this.t1l |= val << 1;
break;
case T1LH:
this.t1l &= 0x1fe;
this.t1l |= val << 9;
Eif (!(this.justhit & 1)) {
this.ifr &= ~TIMER1INT;
this.updateIFR();
}
break;
case T1CH:
this.t1l &= 0x1fe;
this.t1l |= val << 9;
this.t1c = this.t1l + 1;
this.t1hit = false;
Eif (!(this.justhit & 1)) {
this.ifr &= ~TIMER1INT;
this.updateIFR();
}
this.t1_pb7 = 0;
this.updateNextTime();
break;
case T2CL:
this.t2l &= 0x1fe00;
this.t2l |= val << 1;
if (this._t2ClocksShifter()) this.updateNextTime();
break;
case T2CH:
this.t2l &= 0x1fe;
this.t2l |= val << 9;
if (this._t2ClocksShifter()) {
this.t2High = val;
this.t2c = (this.t2l & 0x1fe) + 1;
if (this._shiftUnderWay()) this.shiftTask.reschedule(this._ticksToT2Underflow());
} else {
this.t2c = this.t2l + 1;
if (this.acr & 0x20) this.t2c -= 2;
}
Eif (!(this.justhit & 2)) {
this.ifr &= ~TIMER2INT;
this.updateIFR();
}
this.t2hit = false;
this.updateNextTime();
break;
case IER:
if (val & 0x80) this.ier |= val & 0x7f;
else this.ier &= ~(val & 0x7f);
this.updateIFR();
break;
case IFR:
this.ifr &= ~(val & 0x7f);
Iif (this.justhit & 1) this.ifr |= TIMER1INT;
if (this.justhit & 2) this.ifr |= TIMER2INT;
this.updateIFR();
break;
}
}
read(addr) {
this._catchUp();
switch (addr & 0xf) {
case ORA:
this.ifr &= ~INT_CA1;
Eif ((this.pcr & 0xa) !== 0x2) this.ifr &= ~INT_CA2;
this.updateIFR();
/* falls through */
case ORAnh:
Eif (!(this.acr & 1)) this.recalculatePortAPins();
break;
case ORB:
this.ifr &= ~INT_CB1;
Eif ((this.pcr & 0xa0) !== 0x20) this.ifr &= ~INT_CB2;
this.updateIFR();
this.recalculatePortBPins();
break;
case T1CL:
Eif (!(this.justhit & 1)) {
this.ifr &= ~TIMER1INT;
this.updateIFR();
}
break;
case T2CL:
if (!(this.justhit & 2)) {
this.ifr &= ~TIMER2INT;
this.updateIFR();
}
break;
case SR:
this._accessShiftRegister(false);
break;
}
return this._registerValue(addr);
}
/** Reads a register as the CPU would, without clearing flags or driving the ports: the pins are as last driven. */
peek(addr) {
this._catchUp();
return this._registerValue(addr);
}
/** The timers as 16-bit values, read as {@link peek} would; T2L, which no register reads back, as last written. */
peekTimers() {
const word = (low, high) => (this.peek(high) << 8) | this.peek(low);
return {
t1c: word(T1CL, T1CH),
t1l: word(T1LL, T1LH),
t2c: word(T2CL, T2CH),
t2l: (this.t2l >>> 1) & 0xffff,
};
}
_registerValue(addr) {
switch (addr & 0xf) {
case ORA:
case ORAnh:
// Reading ORA reads pin levels regardless of DDRA.
// Of the various 6522 datasheets, this one is clear:
// http://archive.6502.org/datasheets/wdc_w65c22s_mar_2004.pdf
return this.acr & 1 ? this.ira : this.portapins;
case ORB: {
let temp = this.orb & this.ddrb;
Iif (this.acr & 2) temp |= this.irb & ~this.ddrb;
else temp |= this.portbpins & ~this.ddrb;
// If PB7 is active, it is mixed in regardless of
// whether bit 7 is an input or output.
Iif (this.acr & 0x80) {
temp &= 0x7f;
temp |= this.t1_pb7 << 7;
}
return temp;
}
case DDRA:
return this.ddra;
case DDRB:
return this.ddrb;
case T1LL:
return ((this.t1l & 0x1fe) >>> 1) & 0xff;
case T1LH:
return (this.t1l >>> 9) & 0xff;
case T1CL:
return ((this.t1c + 1) >>> 1) & 0xff;
case T1CH:
return ((this.t1c + 1) >>> 9) & 0xff;
case T2CL:
return ((this.t2c + 1) >>> 1) & 0xff;
case T2CH:
if (this._t2ClocksShifter()) return this.t2High;
return ((this.t2c + 1) >>> 9) & 0xff;
case SR:
return this.sr;
case ACR:
return this.acr;
case PCR:
return this.pcr;
case IER:
return this.ier | 0x80;
case IFR:
return this.ifr;
default:
throw new Error("Unknown VIA read");
}
}
// May be overridden in subclasses
drivePortA() {}
portAUpdated() {}
drivePortB() {}
portBUpdated() {}
rawPortB() {
return 0xff;
}
recalculatePortAPins() {
this.portapins = this.ora & this.ddra;
this.portapins |= ~this.ddra & 0xff;
this.drivePortA();
this.portAUpdated();
}
recalculatePortBPins() {
const prevPb6 = !!(this.portbpins & 0x40);
this.portbpins = (this.orb & this.ddrb) | (~this.ddrb & this.rawPortB());
this.drivePortB();
if (prevPb6 && !(this.portbpins & 0x40)) {
// If we see a high to low transition on pb6, and we are in timer2 pulse counting mode, count a pulse.
if (this._t2CountsPulses()) {
this.t2c -= 2;
// Not clear what happens here. Docs say:
// "When the T2 counter reaches a count of zero, IFR5 is set and the counter continues to decrement with
// each pulse on PB6. To enable IFR5 for subsequent countdowns, it is necessary to reload high order T2
// counter."
Iif (this.t2c < 0) {
this.t2c = 0xffff;
this.ifr |= TIMER2INT;
this.updateIFR();
}
}
}
this.portBUpdated();
}
snapshotState() {
return {
ora: this.ora,
orb: this.orb,
ira: this.ira,
irb: this.irb,
ddra: this.ddra,
ddrb: this.ddrb,
sr: this.sr,
t1l: this.t1l,
t2l: this.t2l,
t1c: this.t1c,
t2c: this.t2c,
acr: this.acr,
pcr: this.pcr,
ifr: this.ifr,
ier: this.ier,
t1hit: this.t1hit,
t2hit: this.t2hit,
t2High: this.t2High,
portapins: this.portapins,
portbpins: this.portbpins,
ca1: this.ca1,
ca2: this.ca2,
cb1: this.cb1,
cb2: this.cb2,
justhit: this.justhit,
t1_pb7: this.t1_pb7,
shiftBits: this.shiftBits,
lastPolltime: this.lastPolltime,
taskOffset: this.task.offset(),
shiftTaskOffset: this.shiftTask.offset(),
ca2PulseTaskOffset: this.ca2PulseTask.offset(),
cb2PulseTaskOffset: this.cb2PulseTask.offset(),
};
}
restoreState(state) {
this.ora = state.ora;
this.orb = state.orb;
this.ira = state.ira;
this.irb = state.irb;
this.ddra = state.ddra;
this.ddrb = state.ddrb;
this.sr = state.sr;
this.t1l = state.t1l;
this.t2l = state.t2l;
this.t1c = state.t1c;
this.t2c = state.t2c;
this.acr = state.acr;
this.pcr = state.pcr;
this.ifr = state.ifr;
this.ier = state.ier;
this.t1hit = state.t1hit;
this.t2hit = state.t2hit;
if (state.t2High !== undefined) this.t2High = state.t2High;
else if (this._t2ClocksShifter()) this._splitT2ForShifting();
else Ethis.t2High = 0;
this.portapins = state.portapins;
this.portbpins = state.portbpins;
this.ca1 = state.ca1;
this.ca2 = state.ca2;
this.cb1 = state.cb1;
this.cb2 = state.cb2;
this.justhit = state.justhit;
this.t1_pb7 = state.t1_pb7;
this.shiftBits = state.shiftBits ?? BitsPerShift;
this.lastPolltime = state.lastPolltime;
this.updateIFR();
this.task.restoreOffset(state.taskOffset);
this.ca2PulseTask.restoreOffset(state.ca2PulseTaskOffset);
this.cb2PulseTask.restoreOffset(state.cb2PulseTaskOffset);
this.shiftTask.restoreOffset(state.shiftTaskOffset);
}
setca1(level) {
Iif (level === this.ca1) return;
const pcrSet = !!(this.pcr & 1);
if (pcrSet === level) {
if (this.acr & 1) this.ira = this.portapins;
this.ifr |= INT_CA1;
this.updateIFR();
if ((this.pcr & 0xc) === 0x8) {
// handshaking
this.setca2(true);
}
}
this.ca1 = level;
}
setca2(level) {
if (level === this.ca2) return;
this.ca2 = level;
const output = !!(this.pcr & 0x08);
if (this.ca2changecallback) this.ca2changecallback(level, output);
if (output) return;
const pcrSet = !!(this.pcr & 4);
if (pcrSet === level) {
this.ifr |= INT_CA2;
this.updateIFR();
}
}
setcb1(level) {
if (level === this.cb1) return;
const pcrSet = !!(this.pcr & 0x10);
if (pcrSet === level) {
if (this.acr & 2) this.irb = this.portbpins;
this.ifr |= INT_CB1;
this.updateIFR();
if ((this.pcr & 0xc0) === 0x80) {
// handshaking
this.setcb2(true);
}
}
this.cb1 = level;
if ((this.acr & AcrShiftExternal) === AcrShiftExternal) this._clockShiftFromCb1(level);
}
setcb2(level) {
if (level === this.cb2) return;
this.cb2 = level;
const output = !!(this.pcr & 0x80);
if (this.cb2changecallback) this.cb2changecallback(level, output);
if (output) return;
const pcrSet = !!(this.pcr & 0x40);
if (pcrSet === level) {
this.ifr |= INT_CB2;
this.updateIFR();
}
}
}
export class SysVia extends WithKeyMatrix(Via) {
constructor(cpu, scheduler, { video, soundChip, cmos, isMaster, initialLayout } = {}) {
super(cpu, scheduler, 0x01);
this.IC32 = 0;
this._initKeyMatrix(BBC.SHIFT, KeyboardColumns);
this.gamepadFire = 0;
this.mouseFire = 0;
this.fireHeld = false;
this.keyChanges = 0;
this.setKeyLayout(initialLayout);
this.video = video;
this.soundChip = soundChip;
this.cmos = cmos;
cmos.replaying = () => cpu.replaying;
this.isMaster = isMaster;
this.keyScanTask = this.scheduler.newTask(() => this.scanPassesHeldKey());
this.reset();
}
reset() {
super.reset();
this.keyScanTask.cancel();
// The keyboard and CMOS drive port A whatever the VIA does, as restoreState() recomputes it.
this.drivePortA();
}
write(addr, val) {
const ca2WasFlagged = this.ifr & INT_CA2;
super.write(addr, val);
this._scanAfterCa2Cleared(ca2WasFlagged);
}
read(addr) {
const ca2WasFlagged = this.ifr & INT_CA2;
const result = super.read(addr);
this._scanAfterCa2Cleared(ca2WasFlagged);
return result;
}
snapshotState() {
return {
...super.snapshotState(),
IC32: this.IC32,
keyScanTaskOffset: this.keyScanTask.offset(),
...(this.isMaster && { cmos: this.cmos.snapshotState() }),
};
}
restoreState(state) {
super.restoreState(state);
this.keyScanTask.restoreOffset(state.keyScanTaskOffset);
this.IC32 = state.IC32;
if (this.isMaster) {
if (state.cmos) this.cmos.restoreState(state.cmos);
else Ethis.cmos.followLines(this.portbpins, this.IC32);
}
this.recalculatePortAPins();
}
get capsLockLight() {
return !(this.IC32 & 0x40);
}
get shiftLockLight() {
return !(this.IC32 & 0x80);
}
setKeyLayout(map) {
this.keycodeToRowCol = getKeyMap(map);
}
setVBlankInt(level) {
this.setca1(level);
}
/** Counted for `machineMoment`. */
_keysChanged() {
++this.keyChanges;
super._keysChanged();
}
updateKeys() {
if (this.IC32 & 8) {
for (let column = 0; column < KeyboardColumns; ++column) {
if (this._columnHasScannedKey(column)) {
// ca2 stands for the whole pulse train here, so a snapshot keeps whether it is running.
if (!this.ca2) {
this.ca2 = true;
this.scanPassesHeldKey();
} else if (this.keyScanTask.scheduled()) {
this._scheduleScanEdge();
}
return;
}
}
this.keyScanTask.cancel();
this.ca2 = false;
return;
} else {
this.keyScanTask.cancel();
// Keyboard sets bit 7 to 0 or 1, and testing shows it always
// "wins" vs. CMOS.
// At 0 also wins against an output pin.
const portapins = this.portapins;
const keyrow = (portapins >>> 4) & 7;
const keycol = portapins & 0xf;
if (!this.keys[keycol][keyrow]) {
this.portapins &= 0x7f;
} else Eif (!(this.ddra & 0x80)) {
this.portapins |= 0x80;
}
if (this._columnHasScannedKey(keycol)) {
this.setca2(true);
return;
}
}
this.setca2(false);
}
/**
* The autoscan putting an edge on CA2 for a held key. A press sets the flag at once whichever edge the PCR selects,
* as the scan's pulses have both.
*/
scanPassesHeldKey() {
if (this.pcr & 0x08) return;
this.ifr |= INT_CA2;
this.updateIFR();
}
_scanAfterCa2Cleared(ca2WasFlagged) {
if (ca2WasFlagged && !(this.ifr & INT_CA2) && this.IC32 & 8 && this.ca2) {
this._scheduleScanEdge();
}
}
/** The column the autoscan counter is on. Its power-on phase is arbitrary, so it is taken from the scheduler epoch. */
scanColumn() {
return Math.floor(this.scheduler.epoch / TicksPerScanColumn) % ScanCounterColumns;
}
/**
* Schedules the flag for the scan's next edge of the kind the PCR selects: rising as the counter moves from a column
* with no key held onto one with a key held, falling the other way.
*/
_scheduleScanEdge() {
this.keyScanTask.cancel();
const epoch = this.scheduler.epoch;
const column = this.scanColumn();
const risingEdge = !!(this.pcr & 0x04);
let leavingHeld = this._columnHasScannedKey(column);
for (let step = 1; step <= ScanCounterColumns; ++step) {
const enteringHeld = this._columnHasScannedKey((column + step) % ScanCounterColumns);
if (enteringHeld !== leavingHeld && enteringHeld === risingEdge) {
this.keyScanTask.schedule(step * TicksPerScanColumn - (epoch % TicksPerScanColumn));
return;
}
leavingHeld = enteringHeld;
}
}
_columnHasScannedKey(column) {
if (column >= KeyboardColumns) return false;
const rows = this.keys[column];
for (let row = 1; row < 8; ++row) {
if (rows[row]) return true;
}
return false;
}
portAUpdated() {
this.updateKeys();
this.soundChip.updateSlowDataBus(this.portapins, !(this.IC32 & 1));
}
rawPortB() {
if (this.fireHeld) return 0xff;
return ~(this.gamepadFire | this.mouseFire) & 0xff;
}
portBUpdated() {
const portbpins = this.portbpins;
const wasAutoscanning = this.IC32 & 8;
if (portbpins & 8) this.IC32 |= 1 << (portbpins & 7);
else this.IC32 &= ~(1 << (portbpins & 7));
// CA2 rests low between the scan's pulses, so switching scan mode starts from there.
if ((wasAutoscanning ^ this.IC32) & 8) this.ca2 = false;
this.video.setScreenHwScroll((this.IC32 >> 4) & 3);
if (this.isMaster) this.cmos.writeControl(portbpins, this.portapins, this.IC32);
// Updating IC32 may have enabled peripherals attached to port A.
this.recalculatePortAPins();
}
drivePortA() {
// For experiments where we tested these behaviors, see:
// https://stardot.org.uk/forums/viewtopic.php?f=4&t=17597
// If either keyboard or CMOS pulls a given pin low, it "wins"
// vs. via output.
let busval = 0xff;
if (this.isMaster) busval &= this.cmos.read(this.IC32);
this.portapins &= busval;
this.updateKeys();
}
drivePortB() {
// Nothing driving here.
// Note that if speech were fitted, it drives bit 7 low.
}
/**
* Latches the gamepads' FIRE buttons, which the page reads once a frame.
* @param {boolean} button1
* @param {boolean} button2
*/
setGamepadFire(button1, button2) {
const fire = (button1 ? JoystickFire1 : 0) | (button2 ? JoystickFire2 : 0);
if (fire === this.gamepadFire) return;
this.gamepadFire = fire;
this.inputLog?.record({ kind: "gamepadFire", button1, button2 });
}
/**
* Set joystick button state (for mouse joystick)
* @param {number} buttonNumber - Button number (0 for button1, 1 for button2)
* @param {boolean} pressed - Whether the button is pressed
*/
setJoystickButton(buttonNumber, pressed) {
const bit = buttonNumber === 0 ? JoystickFire1 : JoystickFire2;
this.mouseFire = pressed ? this.mouseFire | bit : this.mouseFire & ~bit;
this.recalculatePortBPins();
this.inputLog?.record({ kind: "joystickButton", button: buttonNumber, pressed });
}
/** Which FIRE buttons the host holds, as `setGamepadFire` and `setJoystickButton` (by button number) set them. */
fireButtons() {
const held = (bits) => [!!(bits & JoystickFire1), !!(bits & JoystickFire2)];
return { gamepad: held(this.gamepadFire), mouse: held(this.mouseFire) };
}
/** @param {boolean} held whether the FIRE buttons read released whatever is pressed */
holdFireButtons(held) {
this.fireHeld = held;
}
}
export class UserVia extends Via {
constructor(cpu, scheduler, userPortPeripheral) {
super(cpu, scheduler, 0x02);
this.userPortPeripheral = userPortPeripheral;
this.reset();
}
portBUpdated() {
this.userPortPeripheral.write(this.portbpins);
}
drivePortB() {
this.portbpins &= this.userPortPeripheral.read();
}
}
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