diff --git a/cpu.js b/cpu.js
index e985f8c..a2725d3 100644
--- a/cpu.js
+++ b/cpu.js
@@ -4,24 +4,19 @@ const display = require('./display.js');
 
 // STATE
 const CPU = {
+  // Core state
   running: false,
   IP: INITIAL_IP_ADDRESS,
   FLAGS: 0, // A bit field! 0000 = NZOC
   Acc: 0,
   memory: null,
 
-  currentInstruction: {
-    opcode: null,
-    operand: null,
-    mnemonic: null,
-  },
-
+  // Functions that update core state
   /** @param {Uint8Array} data */
   loadMemory: (data) => {
       if (data.length > 256) { throw new Error("Out of memory error (program too long)"); }
       CPU.memory = data;
   },
-
   setFlagNegative: () => { CPU.FLAGS |= 8 },
   setFlagZero:     () => { CPU.FLAGS |= 4 },
   setFlagOverflow: () => { CPU.FLAGS |= 2 },
@@ -30,7 +25,6 @@ const CPU = {
   unsetFlagZero:     () => { CPU.FLAGS &= ~4 },
   unsetFlagOverflow: () => { CPU.FLAGS &= ~2 },
   unsetFlagCarry:    () => { CPU.FLAGS &= ~1 },
-
   updateFlagZero: () => {
     if (CPU.Acc === 0) {
       CPU.setFlagZero();
@@ -38,9 +32,17 @@ const CPU = {
       CPU.unsetFlagZero();
     }
   },
-
   updateFlagNegative: () => {
-    CPU.Acc & 128 ? CPU.setFlagNegative : CPU.unsetFlagNegative },
+    CPU.Acc & 128 ? CPU.setFlagNegative : CPU.unsetFlagNegative
+  },
+
+  // Debug info
+  currentInstruction: {
+    opcode: null,
+    operand: null,
+    mnemonic: null,
+  },
+  cycleCounter: 0,
 }
 
 
@@ -266,17 +268,33 @@ const opcodes2mnemonics = {
  **/
 function startCPU(code) {
   CPU.loadMemory(code);
+  CPU.cycleCounter = 0;
   CPU.running = true;
 }
 
 /**
  * Execute just the next instruction in memory
  **/
-function stepCPU() {
-  CPU.currentInstruction.opcode = CPU.memory[CPU.IP];
-  CPU.currentInstruction.operand = CPU.memory[CPU.IP+1];
-  let executeInstruction = opcodes2mnemonics[CPU.currentInstruction.opcode];
-  executeInstruction(CPU.currentInstruction.operand);
+async function stepCPU(debug = false) {
+  if (CYCLE_LIMIT) { // Temporary limit as a lazy way to halt infinite loops
+    if (CPU.cycleCounter > CYCLE_LIMIT) {
+      console.warn('HALTING - reached cycle limit');
+      CPU.running = false;
+    }
+  }
+  if (CPU.running) {
+    if (CPU.IP >= CPU.memory.length) {
+      console.error('HALTING - IP greater than memory size');
+      CPU.running = false;
+    } else {
+      CPU.currentInstruction.opcode = CPU.memory[CPU.IP];
+      CPU.currentInstruction.operand = CPU.memory[CPU.IP+1];
+      let executeInstruction = opcodes2mnemonics[CPU.currentInstruction.opcode];
+      executeInstruction(CPU.currentInstruction.operand);
+      CPU.cycleCounter += 1;
+    }
+  }
+  await logCPUState(debug);
 }
 
 /**
@@ -285,18 +303,8 @@ function stepCPU() {
  **/
 exports.runProgram = async (code, debug = false) => {
   startCPU(code);
-  let step = 0;
-  while (true) {
-    step = step + 1;
-    // Temporary limit as a lazy way to halt infinite loops:
-    if (CYCLE_LIMIT && (step > CYCLE_LIMIT)) {
-      console.log('SIMULATION HALTING - reached cycle limit');
-      break;
-    }
-    if (!CPU.running) break;
-    if (CPU.IP >= CPU.memory.length) break;
-    stepCPU();
-    await logCPUState(debug);
+  while (CPU.running) {
+    stepCPU(debug);
   };
 }