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Quick change (perhaps temporary) to update LEDs on every WAIT transition (similar to the behavior of the original pdp11.js)

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Jeff Parsons 2016-10-11 10:47:09 -07:00 • committed by Jeff Parsons
commit 4c63c8a97f
1 changed files with 9 additions and 3 deletions
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12
modules/pdp11/lib/cpuops.js
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@ -1692,7 +1692,7 @@ PDP11.opWAIT = function(opCode)
/*
* The original PDP-11 emulation code would actually stop emulating instructions now, relying on assorted
* setTimeout() callbacks, setInterval() callbacks, device XHR (XMLHttpRequest) callbacks, etc, to eventually
* call interrupt(), which would then transition the CPU's runState from 2 to 0 and kickstart emulate() again.
* call interrupt(), which would then transition the CPU of its "wait" state and kickstart emulate() again.
*
* That approach isn't compatible with PCjs emulators, which prefer to rely on the simulated CPU clock to
* drive all simulated device updates. This means components should call the CPU's setTimer() function, which
@ -1703,9 +1703,9 @@ PDP11.opWAIT = function(opCode)
* However, the PCjs approach requires the CPU to continue running. One simple solution to this dilemma:
*
* 1) opWAIT() sets a new opFlags bit (OPFLAG.WAIT)
* 2) Rewind PC back to WAIT
* 2) Rewind the PC back to the WAIT instruction
* 3) Whenever stepCPU() detects OPFLAG.WAIT, call checkInterruptQueue()
* 4) If checkInterruptQueue() detects an interrupt, advance PC past WAIT before dispatching it
* 4) If checkInterruptQueue() detects an interrupt, advance PC past the WAIT and then dispatch the interrupt
*
* Technically, the PC is already exactly where it's supposed to be, so why are we wasting time with steps
* 2 and 4? It's largely for the Debugger's sake, so that as long as execution is "blocked" by a WAIT, that's
@ -1716,6 +1716,12 @@ PDP11.opWAIT = function(opCode)
* check can have a measurable (negative) impact on performance. Which is why it's important to use opFlags bits
* whenever possible, since we can test for multiple (up to 32) exceptional conditions with a single check.
*/
if (!(this.opFlags & PDP11.OPFLAG.WAIT)) {
/*
* Since here we're actually transitioning to WAIT, let's update the Panel's LEDs (well, OK, among other things).
*/
this.cmp.updateStatus();
}
this.opFlags |= PDP11.OPFLAG.WAIT;
this.advancePC(-2);
this.nStepCycles -= 3;