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fix(ALU): correct borrow flag for subtraction and handle CTR=3 stale … #846

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fix(ALU): correct borrow flag for subtraction and handle CTR=3 stale … #846

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8 changes: 7 additions & 1 deletion src/simulator/src/modules/ALU.js
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Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,12 @@ export default class ALU extends CircuitElement {
simulationArea.simulationQueue.add(this.output)
this.message = 'A+B'
} else if (this.controlSignalInput.value === 3) {
// No operation - output 0 to avoid stale data
this.message = 'ALU'
this.output.value = 0
simulationArea.simulationQueue.add(this.output)
this.carryOut.value = 0
simulationArea.simulationQueue.add(this.carryOut)
} else if (this.controlSignalInput.value === 4) {
this.message = 'A&~B'
this.output.value = this.inp1.value & this.flipBits(this.inp2.value)
Expand All @@ -165,7 +170,8 @@ export default class ALU extends CircuitElement {
(32 - this.bitWidth)) >>>
(32 - this.bitWidth)
simulationArea.simulationQueue.add(this.output)
this.carryOut.value = 0
// Borrow flag: set to 1 when B > A (borrow occurred)
this.carryOut.value = +(this.inp1.value < this.inp2.value)
simulationArea.simulationQueue.add(this.carryOut)
} else if (this.controlSignalInput.value === 7) {
this.message = 'A<B'
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8 changes: 7 additions & 1 deletion v1/src/simulator/src/modules/ALU.js
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Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,12 @@ export default class ALU extends CircuitElement {
simulationArea.simulationQueue.add(this.output)
this.message = 'A+B'
} else if (this.controlSignalInput.value === 3) {
// No operation - output 0 to avoid stale data
this.message = 'ALU'
this.output.value = 0
simulationArea.simulationQueue.add(this.output)
this.carryOut.value = 0
simulationArea.simulationQueue.add(this.carryOut)
} else if (this.controlSignalInput.value === 4) {
this.message = 'A&~B'
this.output.value = this.inp1.value & this.flipBits(this.inp2.value)
Expand All @@ -165,7 +170,8 @@ export default class ALU extends CircuitElement {
(32 - this.bitWidth)) >>>
(32 - this.bitWidth)
simulationArea.simulationQueue.add(this.output)
this.carryOut.value = 0
// Borrow flag: set to 1 when B > A (borrow occurred)
this.carryOut.value = +(this.inp1.value < this.inp2.value)
simulationArea.simulationQueue.add(this.carryOut)
} else if (this.controlSignalInput.value === 7) {
this.message = 'A<B'
Expand Down
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