Pop implementation + minor workarounds

HKM-UNI · Nov 19, 2023 · 87a3770 · 87a3770
1 parent 7e027c4
commit 87a3770
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Showing 4 changed files with 54 additions and 8 deletions.
diff --git a/system/cpu/arch.ts b/system/cpu/arch.ts
@@ -1,4 +1,4 @@
-import { Push } from "../instructions/stack.js";
+import { Push, Pop } from "../instructions/stack.js";
 import { Executable } from "./interface.js";
 
 const syntax: { [key: string]: RegExp } = {
@@ -18,7 +18,7 @@ const instructionSet: {
   POP: {
     code: 1,
     type: "transfer",
-    executor: null,
+    executor: new Pop(),
   },
   ADD: {
     code: 2,

diff --git a/system/cpu/execution_unit.ts b/system/cpu/execution_unit.ts
@@ -3,6 +3,7 @@ import { processInfo } from "../memory/data.js";
 import { decodeInstruction } from "../assembler.js";
 import { instructionSet } from "./arch.js";
 import { Instruction, Executable } from "./interface.js";
+import { resetSpOffset } from "../instructions/stack.js";
 
 function fetch(): Instruction | null {
   cpu.MAR = cpu.programCounter;
@@ -54,6 +55,8 @@ function resetRegisters(): void {
   for (const reg of textRegisters) {
     reg.value = "";
   }
+
+  resetSpOffset();
 }
 
 function execute(instruction: Instruction): void {

diff --git a/system/events.ts b/system/events.ts
@@ -4,7 +4,7 @@ import { fetch, execute, resetRegisters } from "./cpu/execution_unit.js";
 
 function run() {
   try {
-    resetRegisters;
+    resetRegisters();
     processInfo.objectCode = makeObjectCode();
     while (true) {
       const ins = fetch();

diff --git a/system/instructions/stack.ts b/system/instructions/stack.ts
@@ -2,18 +2,27 @@ import cpu from "../cpu/components.js";
 import { Instruction, Executable } from "../cpu/interface.js";
 import { getDataByAddress } from "../memory/data.js";
 
+var spOffset = 0;
+
+export function resetSpOffset() {
+  spOffset = 0;
+}
+
 export class Push implements Executable {
   run(instruction: Instruction) {
-    var operandValue = instruction.operand;
-
+    let nextStackPointer = cpu.stackPointer.parseHex() + spOffset;
+    // Workaround when starting at "0000".
+    if (!spOffset) {
+      spOffset = 1;
+    }
+    cpu.stackPointer = nextStackPointer.asHex16();
     const stackData = getDataByAddress("stack-data", cpu.stackPointer)!;
-    const stackPointer = cpu.stackPointer.parseHex();
-    cpu.stackPointer = (stackPointer + 1).asHex16();
 
+    const operandValue = instruction.operand;
     if (!instruction.addressingMode) {
       stackData.value = operandValue.toString();
     } else {
-      const hexOperand = instruction.operand.asHex16();
+      const hexOperand = operandValue.asHex16();
       cpu.MAR = hexOperand;
 
       const actualData = getDataByAddress("main-data", hexOperand)!;
@@ -22,3 +31,37 @@ export class Push implements Executable {
     }
   }
 }
+
+export class Pop implements Executable {
+  run(instruction: Instruction) {
+    if (!instruction.addressingMode) {
+      throw new ReferenceError("You must 'POP' to a variable in main memory");
+    }
+
+    const topOfStack = getDataByAddress("stack-data", cpu.stackPointer)!;
+    if (!topOfStack.value) {
+      throw new ReferenceError("There is no data at the address of the stack pointer.");
+    }
+
+    let nextStackPointer = cpu.stackPointer.parseHex();
+    // Avoids going negative
+    if (nextStackPointer == 0) {
+      resetSpOffset();
+    } else {
+      nextStackPointer -= 1;
+    }
+    cpu.stackPointer = nextStackPointer.asHex16();
+
+    const hexOperand = instruction.operand.asHex16();
+    cpu.MAR = hexOperand;
+    const actualData = getDataByAddress("main-data", hexOperand)!;
+    // cpu.controlUnit = "IR(5-16)out, MARin, READ";
+
+    cpu.MDR = (+topOfStack.value).asHex16();
+    cpu.controlUnit = "SPout, MDRin, WRITE";
+    actualData.value = topOfStack.value;
+
+    topOfStack.variable = "";
+    topOfStack.value = "";
+  }
+}