Retro/pcjs
Watch
1
0
Fork
You've already forked pcjs
 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

New improved PDP-10 processor flag handling

Browse source
This commit is contained in:
Jeff 2017-03-04 21:07:56 -08:00 • committed by Jeff Parsons
commit ffb7fa1221
6 changed files with 287 additions and 263 deletions
Download patch file Download diff file Expand all files Collapse all files

46
modules/pdp10/lib/cpustate.js
View file

@ -178,15 +178,14 @@ class CPUStatePDP10 extends CPUPDP10 {
this.regPC = this.lastPC = this.addrReset;
/*
* This next internal reg is used only with byte instructions, to record an active byte
* pointer state (regPS).
* This next internal reg is used only with byte instructions, to record an active byte pointer.
*/
this.regPS = -1;
this.regBP = -1;
/*
* Assorted processor flags
*/
this.fOverflow = this.fCarry0 = this.fCarry1 = this.fNoDivide = this.fPDOverflow = false;
this.regPS = 0;
/*
* This is queried and displayed by the Panel when it's not displaying its own ADDRESS register
@ -291,13 +290,9 @@ class CPUStatePDP10 extends CPUPDP10 {
this.regRA,
this.regOP,
this.regPC,
this.regBP,
this.regPS,
this.opFlags,
this.fOverflow,
this.fCarry0,
this.fCarry1,
this.fNoDivide,
this.fPDOverflow,
this.lastPC,
this.addrLast,
this.addrReset
@ -327,13 +322,9 @@ class CPUStatePDP10 extends CPUPDP10 {
this.regRA,
this.regOP,
this.regPC,
this.regBP,
this.regPS,
this.opFlags,
this.fOverflow,
this.fCarry0,
this.fCarry1,
this.fNoDivide,
this.fPDOverflow,
this.lastPC,
this.addrLast,
this.addrReset
@ -349,6 +340,19 @@ class CPUStatePDP10 extends CPUPDP10 {
return true;
}
/**
* getPS()
*
* Gets the processor state flags in the format required by various program control operations.
*
* @this {CPUStatePDP10}
* @return {number}
*/
getPS()
{
return this.regPS & PDP10.HALF_MASK;
}
/**
* readFlags()
*
@ -360,8 +364,8 @@ class CPUStatePDP10 extends CPUPDP10 {
readFlags()
{
var flags = 0;
if (this.fOverflow) flags |= PDP10.RFLAG.OVFL;
if (this.fPDOverflow) flags |= PDP10.RFLAG.PDOVFL;
if (this.regPS & PDP10.PSFLAG.OVFL) flags |= PDP10.RFLAG.OVFL;
if (this.regPS & PDP10.PSFLAG.PD_OVFL) flags |= PDP10.RFLAG.PD_OVFL;
return flags;
}
@ -375,8 +379,8 @@ class CPUStatePDP10 extends CPUPDP10 {
*/
writeFlags(w)
{
if (w & PDP10.WFLAG.OVFL_CL) this.fOverflow = false;
if (w & PDP10.WFLAG.PDOVFL_CL) this.fPDOverflow = false;
if (w & PDP10.WFLAG.OVFL_CL) this.regPS &= ~PDP10.PSFLAG.OVFL;
if (w & PDP10.WFLAG.PD_OVFL_CL) this.regPS &= ~PDP10.PSFLAG.PD_OVFL;
}
/**
@ -507,7 +511,7 @@ class CPUStatePDP10 extends CPUPDP10 {
if (src != PDP10.MIN_NEG36) {
src = PDP10.TWO_POW36 - src;
} else {
this.fOverflow = this.fCarry1 = true;
this.regPS |= (PDP10.PSFLAG.OVFL | PDP10.PSFLAG.CARRY1);
}
}
return src;
@ -525,7 +529,7 @@ class CPUStatePDP10 extends CPUPDP10 {
negate(src)
{
if (!src) {
this.fCarry0 = this.fCarry1 = true;
this.regPS |= (PDP10.PSFLAG.CARRY0 | PDP10.PSFLAG.CARRY1);
}
else {
/*
@ -533,7 +537,7 @@ class CPUStatePDP10 extends CPUPDP10 {
* the MIN_NEG36 case anyway, and since subtraction in that case doesn't alter src, we skip the subtraction.
*/
if (src == PDP10.MIN_NEG36) {
this.fOverflow = this.fCarry1 = true;
this.regPS |= (PDP10.PSFLAG.OVFL | PDP10.PSFLAG.CARRY1);
} else {
src = PDP10.TWO_POW36 - src;
}