First commit

src/ProgramCounter.php

@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimAVRPHP;
+
+use SimAVRPHP\Exceptions\InvalidAddressException;
+
+class ProgramCounter
+{
+    private const int RESET_PC_VALUE = 0;
+
+    private int $programCounter = self::RESET_PC_VALUE;
+
+    public function get(): int
+    {
+        return $this->programCounter;
+    }
+
+    public function jump(int $address): void
+    {
+        if (($address % 2) != 0) {
+            throw new InvalidAddressException("Invalid address", $address);
+        }
+
+        $this->programCounter = $address;
+    }
+
+    public function relativeJump(int $address): void
+    {
+        $this->jump($this->programCounter + $address);
+    }
+
+    public function stepWords(int $word): int
+    {
+        $this->programCounter += ($word << 1);
+        return $this->programCounter;
+    }
+
+    public function reset(): void
+    {
+        $this->programCounter = self::RESET_PC_VALUE;
+    }
+}