From a17b7f4ba92ad79227e5254815cc1efae1670637 Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Wed, 26 Jul 2023 11:41:11 +0100
Subject: [PATCH] Start a new simulator sketch with a better architecture +
 using a Uint8Array for memory

---
 sketches/simulator-sketch-v2.js | 130 ++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 sketches/simulator-sketch-v2.js

diff --git a/sketches/simulator-sketch-v2.js b/sketches/simulator-sketch-v2.js
new file mode 100644
index 0000000..d284176
--- /dev/null
+++ b/sketches/simulator-sketch-v2.js
@@ -0,0 +1,130 @@
+// STATE
+
+const CPU = {
+  running: false,
+  IP: 0,
+  CF: 0,
+  Acc: 0,
+  memory: null,
+  loadMemory: (data) => { // data: Uint8Array
+    // TODO: check length of data
+    CPU.memory = data;
+  },
+}
+
+
+// FUNCTIONS THAT MODIFY STATE
+
+const Instructions = {
+  end: () => {
+    console.log('END');
+    CPU.running = false;
+  },
+
+  store_lit: (lit) => {
+    console.log('STO lit#');
+    CPU.memory[lit] = CPU.acc;
+    logTableTitled(CPU.memory, 'Current memory');
+    CPU.IP = CPU.IP += 2;
+  },
+
+  store_addr: (addr) => {
+    console.log('STO addr');
+    CPU.memory[CPU.memory[addr]] = CPU.acc;
+    logTableTitled(CPU.memory, 'Memory');
+    CPU.IP = CPU.IP += 2;
+  },
+
+  load_lit: (lit) => {
+    console.log('LDA lit#');
+    CPU.acc = lit;
+    CPU.IP = CPU.IP += 2;
+  },
+
+  load_addr: (addr) => {
+    console.log('LDA addr');
+    console.log('mem at addr: ', CPU.memory[addr]);
+    CPU.acc = CPU.memory[addr];
+    CPU.IP = CPU.IP += 2;
+  },
+}
+
+const instructionLookupTable = {
+  0: (arg) => Instructions.end(arg),
+  1: (arg) => Instructions.store_lit(arg),
+  2: (arg) => Instructions.store_addr(arg),
+  3: (arg) => Instructions.load_lit(arg),
+  4: (arg) => Instructions.load_addr(arg),
+};
+
+function stepCPU() {
+  console.group("Step CPU");
+  let opcode = CPU.memory[CPU.IP];
+  let argument = CPU.memory[CPU.IP+1];
+
+  console.log(`OP: ${opcode}   ARG: ${argument}`);
+
+  let instruction = instructionLookupTable[opcode];
+  instruction(argument);
+
+  logCPUState();
+  console.groupEnd("Step CPU");
+}
+
+function runCPU() {
+  const initialMemory = JSON.parse(JSON.stringify(CPU.memory)); // Hack to make a copy-by-value -- https://stackoverflow.com/questions/18829099/copy-a-variables-value-into-another
+  console.log();
+  console.log("————————————————————————————————————————");
+  let time = new Date();
+  console.log( `Running at ${time.toLocaleTimeString('en-US')}` );
+  console.log("————————————————————————————————————————");
+  logCPUState();
+
+  CPU.running = true;
+  for (let i = 0; i < 255; i++) { // FIXME: temporary limit as a lazy way to halt infinite loops
+    if (!CPU.running) break;
+    if (CPU.IP >= CPU.memory.length) break;
+    stepCPU();
+  };
+}
+
+
+// FUNCTIONS THAT PULL INFO FROM STATE TO DISPLAY
+
+function logCPUState() {
+  console.log();
+  console.group('CPU state');
+  console.log( `Acc: ${CPU.acc}   IP: ${CPU.IP}   CF: ${CPU.CF}   ${CPU.running ? "running" : "halted" }` );
+  console.log();
+  console.groupEnd('CPU state');
+};
+
+
+// FUNCTIONS FOR DISPLAYING DATA
+
+function num2hex(num) { num.toString(16) };
+function hex2num(hex) { parseInt(hex, 16) };
+
+logTableTitled = (memory, tableTitle) => {
+  console.log();
+  console.group(tableTitle);
+  console.table(memory);
+  console.groupEnd(tableTitle);
+};
+
+
+// RUN IT !
+
+const test_lda_sto = new Uint8Array([
+  3, 17, // LDA lit  ... acc = 17
+  1, 14, // STO lit  ... @14 = acc = 17
+  3, 16, // LDA lit  ... acc = 16
+  1, 15, // STO lit  ... @15 = acc = 16
+  2, 15, // STO addr ... @[@15] = acc = 16 ... mem[mem[addr]] <- Acc
+  4, 0, // LDA addr ... acc = @00 = 03
+  0, 0, // END
+  0, 0, // DATA
+]);
+
+CPU.loadMemory(test_lda_sto);
+runCPU();
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