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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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Jeff Parsons 2017-08-23 10:49:35 -07:00 • committed by Jeff Parsons
commit 157319a355
9 changed files with 754 additions and 669 deletions
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92
modules/pc8080/lib/cpu.js
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@ -900,29 +900,55 @@ 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)
*
@ -948,18 +974,19 @@ 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;
@ -988,12 +1015,12 @@ class CPU8080 extends Component {
*/
getBurstCycles(nCycles)
{
for (var i = this.aTimers.length - 1; i >= 0; i--) {
var timer = this.aTimers[i];
this.assert(!isNaN(timer[0]));
if (timer[0] < 0) continue;
if (nCycles > timer[0]) {
nCycles = timer[0];
for (var iTimer = this.aTimers.length - 1; iTimer >= 0; iTimer--) {
var timer = this.aTimers[iTimer];
this.assert(!isNaN(timer[1]));
if (timer[1] < 0) continue;
if (nCycles > timer[1]) {
nCycles = timer[1];
}
}
return nCycles;
@ -1011,14 +1038,23 @@ class CPU8080 extends Component {
*/
updateTimers(nCycles)
{
for (var i = this.aTimers.length - 1; i >= 0; i--) {
var timer = this.aTimers[i];
this.assert(!isNaN(timer[0]));
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
for (var iTimer = this.aTimers.length - 1; iTimer >= 0; iTimer--) {
var timer = this.aTimers[iTimer];
this.assert(!isNaN(timer[1]));
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)");
}
}
}
}
}