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Fixed the PC11 component to deliver bytes at (roughly) the same rate as a physical "high speed" paper tape reader would (TODO: Add a paper tape status display)

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Jeff Parsons 2016-10-19 11:31:43 -07:00 • committed by Jeff Parsons
commit bff199ee7f
3 changed files with 153 additions and 152 deletions
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33
modules/pdp11/lib/pc11.js
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@ -714,23 +714,12 @@ PC11.prototype.advanceReader = function()
if (!(this.prs & PDP11.PC11.PRS.DONE)) {
if (this.iTapeData < this.aTapeData.length) {
this.prb = this.aTapeData[this.iTapeData++] & 0xff;
if (MAXDEBUG) this.println("tape read " + str.toHexByte(this.prb) + " at pos " + str.toHexWord(this.iTapeData));
this.prs |= PDP11.PC11.PRS.DONE;
this.prs &= ~PDP11.PC11.PRS.BUSY;
if (this.prs & PDP11.PC11.PRS.RIE) {
this.cpu.setTrigger(this.triggerReaderInterrupt);
}
/*
* The PC11, by virtue of its "high speed", is supposed to deliver characters at 300 CPS, so
* that's the rate we'll choose as well (ie, 1000ms / 300). As an aside, the original "low speed"
* version of the reader ran at 10 CPS.
*
* TODO: Review this code. If we don't set the fReset parameter to true, the timer will eventually
* fire while the "Absolute Loader" tape is still reading bytes from, say, the "BASIC (Single User)"
* tape, causing an EXTRA advance to occur and a byte to be skipped. Passing true ensures that the
* timer cannot fire for AT LEAST 3ms after each advance. But we need to understand the reader's
* actual behavior.
*/
this.cpu.setTimer(this.timerReaderAdvance, 1000/300, true);
}
}
}
@ -763,19 +752,31 @@ PC11.prototype.readPRS = function(addr)
PC11.prototype.writePRS = function(data, addr)
{
if (data & PDP11.PC11.PRS.RE) {
/*
* From the 1976 Peripherals Handbook, p. 4-378:
*
* Set [RE] to allow the Reader to fetch one character. The setting of this bit clears Done,
* sets Busy, and clears the Reader Buffer (PRB). Operation of this bit is disabled if Error = 1;
* attempting to set it when Error = 1 will cause an immediate interrupt if Interrupt Enable = 1.
*/
if (this.prs & PDP11.PC11.PRS.ERROR) {
data &= ~PDP11.PC11.PRS.RE;
// if (this.prs & PDP11.PC11.PRS.RIE) {
// TODO: Generate an interrupt (error condition)
// }
if (this.prs & PDP11.PC11.PRS.RIE) {
this.cpu.setTrigger(this.triggerReaderInterrupt);
}
} else {
this.prs &= ~PDP11.PC11.PRS.DONE;
this.prs |= PDP11.PC11.PRS.BUSY;
this.prb = 0;
/*
* The PC11, by virtue of its "high speed", is supposed to deliver characters at 300 CPS, so
* that's the rate we'll choose as well (ie, 1000ms / 300). As an aside, the original "low speed"
* version of the reader ran at 10 CPS.
*/
this.cpu.setTimer(this.timerReaderAdvance, 1000/300);
}
}
this.prs = (this.prs & ~PDP11.PC11.PRS.WMASK) | (data & PDP11.PC11.PRS.WMASK);
this.advanceReader();
};
/**