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Fixed RTI on older PDP-11s (ie, 11/20); the old RTI behaves like the new RTT, which did not exist on older machines

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Jeff 2016-11-13 21:17:46 -08:00 • committed by Jeff Parsons
commit 0607d65b70
8 changed files with 163 additions and 140 deletions
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11
modules/pdp11/lib/cpuops.js
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@ -1507,7 +1507,12 @@ PDP11.opRTI = function(opCode)
{
this.trapReturn();
/*
* Unlike RTT, RTI enables immediate trace
* Unlike RTT, RTI permits an immediate trace, which we resolve by propagating PSW.TF to OPFLAG.TRAP_TF
* (which, as written, requires that both flags have the same bit value; see defines.js).
*
* NOTE: This trace behavior is NEW for machines that have both RTI and RTT. Early models didn't have RTT; ie,
* the old RTI instruction behaved exactly like the new RTT instruction. This is why the 11/20 jump table below
* for RTI calls opRTT() instead of opRTI().
*/
this.opFlags |= (this.regPSW & PDP11.PSW.TF);
this.nStepCycles -= (10 + 3);
@ -1528,7 +1533,7 @@ PDP11.opRTS = function(opCode)
var src = this.popWord();
var reg = opCode & PDP11.OPREG.MASK;
/*
* When the popular "RTS PC" form is used, we might as well eliminate the useless setting of PC to
* When the popular "RTS PC" form is used, we might as well eliminate the useless setting of PC
*/
if (reg == PDP11.REG.PC) {
this.setPC(src);
@ -2057,7 +2062,7 @@ PDP11.aOp00Xn_1120 = [
PDP11.aOp000X_1120 = [
PDP11.opHALT, // 0x0000 000000 11/20+ 1.8
PDP11.opWAIT, // 0x0001 000001 11/20+ 1.8
PDP11.opRTI, // 0x0002 000002 11/20+ 4.8
PDP11.opRTT, // 0x0002 000002 11/20+ 4.8 (this is really RTI, but on the 11/20, it behaves like RTT)
PDP11.opBPT, // 0x0003
PDP11.opIOT, // 0x0004 000004 11/20+ 9.3
PDP11.opRESET, // 0x0005 000005 11/20+ 20ms