examine and examineNext logic

index.html

@@ -211,6 +211,17 @@ db ff d3 ff c3 00 00       // Switch echo between A2 and A1.
        dumpMemElem.innerHTML = dumpHtml;
      }
 
+     function getInputWord() {
+       var word = 0;
+       for (let i = 0; i < 16; i++) {
+         var switchElem = document.getElementById('s' + i);
+         if (switchElem.checked) {
+           word |= 1 << i;
+         }
+       }
+       return word;
+     }
+
      var sim = new Sim8800(256, 1000000,
                            setAddressLedsCallback, setDataLedsCallback,
                            setWaitLedCallback, setStatusLedsCallback,
@@ -244,6 +255,15 @@ db ff d3 ff c3 00 00       // Switch echo between A2 and A1.
      function stop() {
        sim.stop();
      }
+
+     function examine() {
+       var address = getInputWord();
+       sim.examine(address);
+     }
+
+     function examineNext() {
+       sim.examineNext();
+     }
     </script>
   </body>
 </html>

js/sim8800.js

@@ -51,6 +51,7 @@ class Sim8800 {
         this.dumpMemCallback = dumpMemCallback;
         this.isPoweredOn = false;
         this.isRunning = false;
+        this.lastAddress = 0;
         this.initMem();
         CPU8080.init(this.getWriteByteCallback(),
                      this.getReadByteCallback(),
@@ -313,6 +314,7 @@ class Sim8800 {
             return;
         CPU8080.reset();
         this.stop();
+        this.lastAddress = 0;
         if (this.setAddressLedsCallback) {
             this.setAddressLedsCallback(new Array(16).fill(1));
         }
@@ -368,9 +370,37 @@ class Sim8800 {
         this.dumpCpu();
         this.dumpMem();
         if (this.setAddressLedsCallback) {
-            var cpu = CPU8080.status();
+            let cpu = CPU8080.status();
-            var pcBits = Sim8800.parseBits(cpu.pc, 16);
+            let bits = Sim8800.parseBits(cpu.pc, 16);
-            this.setAddressLedsCallback(pcBits);
+            this.setAddressLedsCallback(bits);
         }
     }
+
+    /**
+     * Reads a byte from the given address.
+     * @param {number} address The given address.
+     */
+    examine(address) {
+        if (!this.isPoweredOn)
+            return;
+        this.lastAddress = address;
+        if (this.setAddressLedsCallback) {
+            let bits = Sim8800.parseBits(address, 16);
+            this.setAddressLedsCallback(bits);
+        }
+        if (this.setDataLedsCallback) {
+            let bits = Sim8800.parseBits(this.mem[address], 8);
+            this.setDataLedsCallback(bits);
+        }
+    }
+
+    /**
+     * Reads a byte from the next address.
+     */
+    examineNext() {
+        if (!this.isPoweredOn)
+            return;
+        this.lastAddress++;
+        this.examine(this.lastAddress);
+    }
 };