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Added timer support to the PCx86 SerialPort component, so that we can honor the programmed baud rate now

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This commit is contained in:
Jeff Parsons 2017-08-23 10:50:31 -07:00 • committed by Jeff Parsons
commit 6a3498e666
10 changed files with 800 additions and 714 deletions
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versions/pc8080/1.36.2/pc8080-dbg.js
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versions/pc8080/1.36.2/pc8080-uncompiled.js
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@ -7131,29 +7131,55 @@ class CPU8080 extends Component {
}
/**
* addTimer(callBack)
* addTimer(id, callBack, ms)
*
* Components that want to have timers that periodically fire after some number of milliseconds call
* addTimer() to create the timer, and then setTimer() every time they want to arm it. There is currently
* Components that want to have timers that fire after some number of milliseconds call addTimer() to create
* the timer, and then setTimer() when they want to arm it. Alternatively, they can specify an automatic timeout
* value (in milliseconds) to have the timer fire automatically at regular intervals. There is currently
* no removeTimer() because these are generally used for the entire lifetime of a component.
*
* Internally, each timer entry is a preallocated Array with two entries: a cycle countdown in element [0]
* and a callback function in element [1]. A timer is initially dormant; dormant timers have a countdown
* value of -1 (although any negative number will suffice) and active timers have a non-negative value.
* Internally, each timer entry is a preallocated Array with the following entries:
*
* [0]: timer ID
* [1]: countdown value, in cycles
* [2]: automatic setTimer value, if any, in milliseconds
* [3]: callback function
*
* A timer is initially dormant; dormant timers have a countdown value of -1 (although any negative number
* will suffice) and active timers have a non-negative value.
*
* Why not use JavaScript's setTimeout() instead? Good question. For a good answer, see setTimer() below.
*
* @this {CPU8080}
* @param {string} id
* @param {function()} callBack
* @param {number} [ms] (if set, enables automatic setTimer calls)
* @return {number} timer index
*/
addTimer(callBack)
addTimer(id, callBack, ms = -1)
{
var iTimer = this.aTimers.length;
this.aTimers.push([-1, callBack]);
this.aTimers.push([id, -1, ms, callBack]);
if (ms >= 0) this.setTimer(iTimer, ms);
return iTimer;
}
/**
* findTimer(id)
*
* @this {CPU8080}
* @param {string} id
* @return {Array|null}
*/
findTimer(id)
{
for (var iTimer = 0; iTimer < this.aTimers.length; iTimer++) {
var timer = this.aTimers[iTimer];
if (timer[0] == id) return timer;
}
return null;
}
/**
* setTimer(iTimer, ms, fReset)
*
@ -7179,18 +7205,19 @@ class CPU8080 extends Component {
{
var nCycles = -1;
if (iTimer >= 0 && iTimer < this.aTimers.length) {
if (fReset || this.aTimers[iTimer][0] < 0) {
var timer = this.aTimers[iTimer];
if (fReset || timer[1] < 0) {
nCycles = this.getMSCycles(ms);
/*
* We must now confront the following problem: if the CPU is currently executing a burst of cycles,
* the number of cycles it has executed in that burst so far must NOT be charged against the cycle
* timeout we're about to set. The simplest way to resolve that is to immediately call endBurst()
* and bias the above cycle timeout by the number of cycles that the burst executed.
* If the CPU is currently executing a burst of cycles, the number of cycles it has executed in
* that burst so far must NOT be charged against the cycle timeout we're about to set. The simplest
* way to resolve that is to immediately call endBurst() and bias the cycle timeout by the number
* of cycles that the burst executed.
*/
if (this.flags.running) {
nCycles += this.endBurst();
}
this.aTimers[iTimer][0] = nCycles;
timer[1] = nCycles;
}
}
return nCycles;
@ -7219,12 +7246,12 @@ class CPU8080 extends Component {
*/
getBurstCycles(nCycles)
{
for (var i = this.aTimers.length - 1; i >= 0; i--) {
var timer = this.aTimers[i];
for (var iTimer = this.aTimers.length - 1; iTimer >= 0; iTimer--) {
var timer = this.aTimers[iTimer];
if (timer[0] < 0) continue;
if (nCycles > timer[0]) {
nCycles = timer[0];
if (timer[1] < 0) continue;
if (nCycles > timer[1]) {
nCycles = timer[1];
}
}
return nCycles;
@ -7242,14 +7269,23 @@ class CPU8080 extends Component {
*/
updateTimers(nCycles)
{
for (var i = this.aTimers.length - 1; i >= 0; i--) {
var timer = this.aTimers[i];
for (var iTimer = this.aTimers.length - 1; iTimer >= 0; iTimer--) {
var timer = this.aTimers[iTimer];
if (timer[0] < 0) continue;
timer[0] -= nCycles;
if (timer[0] <= 0) {
timer[0] = -1; // zero is technically an "active" value, so ensure the timer is dormant now
timer[1](); // safe to invoke the callback function now
if (timer[1] < 0) continue;
timer[1] -= nCycles;
if (timer[1] <= 0) {
if (DEBUG && this.messageEnabled(Messages8080.CPU)) {
this.printMessage("updateTimer(" + nCycles + "): firing " + timer[0] + " with only " + (timer[1] + nCycles) + " cycles left");
}
timer[1] = -1; // zero is technically an "active" value, so ensure the timer is dormant now
timer[3](); // safe to invoke the callback function now
if (timer[2] >= 0) {
this.setTimer(iTimer, timer[2]);
if (DEBUG && this.messageEnabled(Messages8080.CPU)) {
this.printMessage("updateTimer(" + nCycles + "): rearming " + timer[0] + " for " + timer[2] + "ms (" + timer[1] + " cycles)");
}
}
}
}
}
@ -13588,7 +13624,7 @@ class Keyboard8080 extends Component {
this.dbg = dbg; // NOTE: The "dbg" property must be set for the message functions to work
var kbd = this;
this.timerReleaseKeys = this.cpu.addTimer(function() {
this.timerReleaseKeys = this.cpu.addTimer(this.id, function() {
kbd.checkSoftKeysToRelease();
});
@ -15167,7 +15203,7 @@ class Video8080 extends Component {
}
var video = this;
this.timerUpdateNext = this.cpu.addTimer(function() {
this.timerUpdateNext = this.cpu.addTimer(this.id, function() {
video.updateScreen();
});
this.cpu.setTimer(this.timerUpdateNext, this.getRefreshTime());
@ -16593,10 +16629,10 @@ class SerialPort8080 extends Component {
this.dbg = dbg;
var serial = this;
this.timerReceiveNext = this.cpu.addTimer(function() {
this.timerReceiveNext = this.cpu.addTimer(this.id + ".receive", function() {
serial.receiveData();
});
this.timerTransmitNext = this.cpu.addTimer(function() {
this.timerTransmitNext = this.cpu.addTimer(this.id + ".transmit", function() {
serial.transmitData();
});
@ -16803,8 +16839,8 @@ class SerialPort8080 extends Component {
var nBits = ((this.bMode & SerialPort8080.UART8251.MODE.DATA_BITS) >> 2) + 6; // includes an extra +1 for start bit
if (this.bMode & SerialPort8080.UART8251.MODE.PARITY_ENABLE) nBits++;
nBits += ((((this.bMode & SerialPort8080.UART8251.MODE.STOP_BITS) >> 6) + 1) >> 1);
var nBytesPerSecond = Math.round(nBaud / nBits);
return 1000 / nBytesPerSecond;
var nBytesPerSecond = nBaud / nBits;
return (1000 / nBytesPerSecond)|0;
}
/**
@ -16900,11 +16936,9 @@ class SerialPort8080 extends Component {
}
}
if (this.sendData) {
if (this.sendData.call(this.connection, b)) {
if (this.sendData && this.sendData.call(this.connection, b)) {
fTransmitted = true;
}
}
if (this.echoByte(b)) {
fTransmitted = true;
@ -16921,6 +16955,10 @@ class SerialPort8080 extends Component {
* When timerTransmitNext fires, we have honored the programmed XMIT_RATE period, so we can
* set XMIT_READY (and XMIT_EMPTY), which signals the firmware that another byte can be transmitted.
*
* The sData parameter is not used when we're called via the timer; it's an optional parameter used by
* the Keyboard component to deliver data pasted via the clipboard, and is currently only useful when
* the SerialPort is connected to another machine. TODO: Define a separate interface for that feature.
*
* @this {SerialPort8080}
* @param {string} [sData]
* @return {boolean} true if successful, false if not

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versions/pcx86/1.36.2/pcx86-uncompiled.js
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@ -7668,8 +7668,8 @@ class Panel extends Component {
* startTimer()
*
* This timer replaces the CPU's old dedicated VIDEO_UPDATES_PER_SECOND logic, which periodically called
* the Computer's updateVideo() function, which in turn called us; periodic updateAnimation() calls are now
* our own responsibility.
* the Computer's updateVideo() function, which in turn called our updateAnimation() function; periodic
* animation updates are now our own responsibility.
*
* @this {Panel}
*/
@ -12640,11 +12640,12 @@ class CPU extends Component {
* value (in milliseconds) to have the timer fire automatically at regular intervals. There is currently
* no removeTimer() because these are generally used for the entire lifetime of a component.
*
* Internally, each timer entry is a preallocated Array with three entries:
* Internally, each timer entry is a preallocated Array with the following entries:
*
* [0]: countdown value, in cycles
* [1]: automatic setTimer value, if any, in milliseconds
* [2]: callback function
* [0]: timer ID
* [1]: countdown value, in cycles
* [2]: automatic setTimer value, if any, in milliseconds
* [3]: callback function
*
* A timer is initially dormant; dormant timers have a countdown value of -1 (although any negative number
* will suffice) and active timers have a non-negative value.
@ -55094,8 +55095,11 @@ class SerialPort extends Component {
*
* binding: name of a control (based on its "binding" attribute) to bind to this port's I/O
*
* tabSize: set to a non-zero number to convert tabs to spaces (applies only to output to
* the above binding); default is 0 (no conversion)
* tabSize: a non-zero number specifies the tab-stop multiple to use for automatic tab-to-space
* conversion; it applies only to the above binding, and the default is 0 (no tab conversion)
*
* charBOL: a non-zero number specifies the ASCII code of a character to display at the beginning
* of every line; it applies only to the above binding, and the default is 0 (no BOL character)
*
* In the future, we may support 'port' and 'irq' properties that allow the machine to define a non-standard
* serial port configuration, instead of only our pre-defined 'adapter' configurations.
@ -55158,11 +55162,12 @@ class SerialPort extends Component {
* being echoed via transmitByte(), maintain a logical column position, and convert any tabs into the appropriate
* number of spaces.
*
* charBOL, if nonzero, is a character to automatically output at the beginning of every line. This probably
* isn't generally useful; I use it internally to preformat serial output.
* Another controlIOBuffer feature is charBOL, which, if nonzero, specifies a character to automatically output
* at the beginning of every line. This probably isn't generally useful; I use it internally to preformat serial
* output.
*/
this.tabSize = parmsSerial['tabSize'];
this.charBOL = parmsSerial['charBOL'];
this.tabSize = parmsSerial['tabSize'] || 0;
this.charBOL = parmsSerial['charBOL'] || 0;
this.charPrev = 0;
this.iLogicalCol = 0;
@ -55310,6 +55315,14 @@ class SerialPort extends Component {
this.cpu = cpu;
this.dbg = dbg;
var serial = this;
this.timerReceiveNext = this.cpu.addTimer(this.id + ".receive", function() {
serial.receiveData();
});
this.timerTransmitNext = this.cpu.addTimer(this.id + ".transmit", function() {
serial.transmitData();
});
this.chipset = cmp.getMachineComponent("ChipSet");
bus.addPortInputTable(this, SerialPort.aPortInput, this.portBase);
@ -55331,7 +55344,7 @@ class SerialPort extends Component {
*
* For now, we're not going to worry about communication in the other direction, because when the target component
* performs its own initConnection(), it will find our receiveData() and receiveStatus() functions, at which point
* communication in both directions should be established, and the circle of life complete.
* communication in both directions should be established, and the circle of life is complete.
*
* For added robustness, if the target machine initializes much more slowly than we do, and our connection attempt
* fails, that's OK, because when it finally initializes, its initConnection() will call our initConnection();
@ -55520,19 +55533,38 @@ class SerialPort extends Component {
return data;
}
/**
* getBaudTimeout()
*
* The 16-bit Divisor Latch is stored in wDL. If we take the frequency value 1843200 and divide it by wDL*128,
* we get the maximum number of bytes per second that the SerialPort interface should generate. For example,
* if a baud rate of 1200 is being used, the divisor will be 0x60 (96), so we calculate 1843200/(96*128) = 150,
* which means there should be a 1000ms/150 or 6.667ms delay between bytes delivered.
*
* @this {SerialPort}
* @return {number} (number of milliseconds per byte)
*/
getBaudTimeout()
{
var nBytesPerSecond = 1843200 / ((this.wDL || 1) << 7);
return (1000 / nBytesPerSecond)|0;
}
/**
* receiveData(data)
*
* This replaces the old sendRBR() function, which expected an Array of bytes. We still support that,
* but in order to support connections with other SerialPort components (ie, the PC8080 SerialPort), we
* have added support for numbers and strings as well.
* have added support for numbers and strings as well. If no data is specified at all, then all we do is
* "clock" any remaining data into the receiver.
*
* @this {SerialPort}
* @param {number|string|Array} data
* @param {number|string|Array} [data]
* @return {boolean} true if received, false if not
*/
receiveData(data)
{
if (data != null) {
if (typeof data == "number") {
this.abReceive.push(data);
}
@ -55544,6 +55576,7 @@ class SerialPort extends Component {
else {
this.abReceive = this.abReceive.concat(data);
}
}
this.advanceRBR();
return true; // for now, return true regardless, since we're buffering everything anyway
}
@ -55551,9 +55584,9 @@ class SerialPort extends Component {
/**
* receiveStatus(pins)
*
* NOTE: Prior to the addition of this interface, the CTS and DSR bits were initialized set and remained set for the life
* of the machine. It is entirely appropriate that this is the only way those bits can be changed, because they represent
* external control signals.
* NOTE: Prior to the addition of this interface, the CTS and DSR bits were initialized set and remained set
* for the life of the machine. It is entirely appropriate that this is the only way those bits can be changed,
* because they represent external control signals.
*
* @this {SerialPort}
* @param {number} pins
@ -55581,6 +55614,9 @@ class SerialPort extends Component {
if (this.abReceive.length > 0 && !(this.bLSR & SerialPort.LSR.DR)) {
this.bRBR = this.abReceive.shift();
this.bLSR |= SerialPort.LSR.DR;
if (this.abReceive.length && this.cpu) {
this.cpu.setTimer(this.timerReceiveNext, this.getBaudTimeout());
}
}
this.updateIRR();
}
@ -55719,7 +55755,16 @@ class SerialPort extends Component {
this.bTHR = bOut;
this.bLSR &= ~(SerialPort.LSR.THRE | SerialPort.LSR.TSRE);
if (this.transmitByte(bOut)) {
this.bLSR |= (SerialPort.LSR.THRE | SerialPort.LSR.TSRE);
/*
* If we're transmitting to a virtual device that has no measurable delay, this code may set the
* transmitter empty bits too quickly:
*
* this.bLSR |= (SerialPort.LSR.THRE | SerialPort.LSR.TSRE);
*
* A better solution is to arm a timer based on the baud rate, and clear the above bits when that
* timer fires.
*/
if (this.cpu) this.cpu.setTimer(this.timerTransmitNext, this.getBaudTimeout());
this.updateIRR();
/*
* QUESTION: Does this mean we should also flush/zero bTHR?
@ -55815,8 +55860,24 @@ class SerialPort extends Component {
this.bIIR &= ~(SerialPort.IIR.NO_INT | SerialPort.IIR.INT_BITS);
this.bIIR |= bIIR;
/*
* TODO: Remove this arbitrary 100-instruction delay once we've added support for baud rate throttling
* (see notes above regarding baud rate).
* I still throttle SerialPort interrupts by passing a hard-coded delay of 100 instructions to setIRR(),
* even though we are now (theoretically) honoring the programmed baud rate. The setIRR() delay does not
* ensure any particular baud rate, it simply gives the underlying Interrupt Service Routine (ISR) some
* breathing room.
*
* The Microsoft Windows 1.01 serial mouse driver ISR issues an EOI before it has safely exited, presumably
* relying on the fact that a 1200 baud serial device would not normally interrupt frequently enough to
* blow the stack. However, in PCx86, all you have to do is remove the delay below and enable Debugger
* messages on every serial interrupt and mouse event, eg:
*
* m serial on;m pic on;m mouse on
*
* to slow the machine down to the point where serial mouse interrupts overwhelm the ISR. The Debugger
* messages display the current stack pointer, which you can watch drop to zero and then wrap around, no
* doubt trampling lots of code and data along the way.
*
* This problem could also occur without being forced by the Debugger; eg, if your physical machine's mouse
* was configured for a high interrupt rate, and your browser generated mouse events at a comparable rate.
*/
if (this.chipset && this.nIRQ) this.chipset.setIRR(this.nIRQ, 100);
} else {
@ -55893,6 +55954,18 @@ class SerialPort extends Component {
return fTransmitted;
}
/**
* transmitData()
*
* Helper for clocking transmitted data at the expected baud rate.
*
* @this {SerialPort}
*/
transmitData()
{
this.bLSR |= (SerialPort.LSR.THRE | SerialPort.LSR.TSRE);
}
/**
* SerialPort.init()
*
@ -55958,34 +56031,6 @@ SerialPort.DLL = {REG: 0}; // Divisor Latch LSB (only when SerialPo
SerialPort.THR = {REG: 0}; // Transmitter Holding Register (write)
SerialPort.DL_DEFAULT = 0x180; // we select an arbitrary default Divisor Latch equivalent to 300 baud
/*
* The divisor is stored in wDL. If we take the frequency value 1843200 and divide it by wDL*128, we get the
* maximum number of bytes per second that the SerialPort interface should generate. For example, if a baud
* rate of 1200 is being used, the divisor will be 0x60 (96), so we calculate 1843200/(96*128) = 150, which means
* there should be a 1000ms/150 or 6.667ms delay between bytes delivered.
*
* TODO: Enforce that delay. However, the delay should be converted from real-world milliseconds to the
* appropriate number of CPU cycles we can pass to setBurstCycles(). This will also require the CPU to call
* us at the start of each burst, to see if advanceRBR() has more data to deliver. For now, I'm throttling
* SerialPort interrupts by passing a hard-coded delay to setIRR(). The setIRR() delay does not ensure any
* particular baud rate, it simply gives the underlying Interrupt Service Routine (ISR) some breathing room.
*
* The Microsoft Windows 1.01 serial mouse driver ISR issues an EOI before it has safely exited, presumably
* relying on the fact that a 1200 baud serial device would not normally interrupt frequently enough to blow
* the stack. However, in PCx86, all you have to do is enable Debugger messages on every serial interrupt
* and mouse event, eg:
*
* m serial on;m pic on;m mouse on
*
* to slow the machine down to the point where serial mouse interrupts overwhelm the ISR. The Debugger messages
* display the current stack pointer, which you can watch drop to zero and then wrap around, no doubt trampling
* lots of code and data along the way.
*
* This problem could also occur without being forced by the Debugger; eg, if your physical machine's mouse was
* configured for a high interrupt rate, and your browser generated mouse events at a comparable rate, then you
* could blow the simulation's stack.
*/
/*
* Receiver Buffer Register (RBR.REG, offset 0; eg, 0x3F8 or 0x2F8) on read, Transmitter Holding Register on write
*/
@ -56050,8 +56095,9 @@ SerialPort.MCR.UNUSED = 0xE0; // always zero
/*
* Line Status Register (LSR.REG, offset 5; eg, 0x3FD or 0x2FD)
*
* NOTE: I've seen different specs for the LSR_TSRE. I'm following the IBM Tech Ref's lead here, but the data sheet I have calls it TEMT
* instead of TSRE, and claims that it is set whenever BOTH the THR and TSR are empty, and clear whenever EITHER the THR or TSR contain data.
* NOTE: I've seen different specs for the LSR_TSRE. I'm following the IBM Tech Ref's lead here, but the data sheet
* I have calls it TEMT instead of TSRE, and claims that it is set whenever BOTH the THR and TSR are empty, and clear
* whenever EITHER the THR or TSR contain data.
*/
SerialPort.LSR = {};
SerialPort.LSR.REG = 5; // Line Status Register

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