1 files changed, 29 insertions, 1 deletions
diff --git a/src/cpu/cpu.ts b/src/cpu/cpu.ts
index 4065b0a..6da0fee 100644
--- a/src/cpu/cpu.ts
+++ b/src/cpu/cpu.ts
@@ -59,6 +59,21 @@ export class CPU {
    */
   readonly pc22Bits = this.progBytes.length > 0x20000;
 
+  /**
+   * Offset applied to data-space addresses in readData/writeData.
+   * Classic AVR (ATmega): 0 — data addresses map 1:1 to the data array.
+   * Modern AVR (AVR-Dx, avrxmega3): 32 — data addresses are shifted by 32
+   * to avoid collision with R0-R31 which occupy data[0..31].
+   */
+  readonly dataMemoryOffset: number;
+
+  /**
+   * Offset added to I/O addresses for IN/OUT/SBI/CBI/SBIS/SBIC instructions.
+   * Classic AVR (ATmega): 32 — I/O space starts at data address 0x20.
+   * Modern AVR (AVR-Dx): 0 — readData applies dataMemoryOffset instead.
+   */
+  readonly ioOffset: number;
+
   readonly gpioPorts = new Set<AVRIOPort>();
   readonly gpioByPort: AVRIOPort[] = [];
 
@@ -71,6 +86,14 @@ export class CPU {
   };
 
   /**
+   * This function is called by the SLEEP instruction. The sleep controller peripheral
+   * attaches to it to handle sleep modes (e.g., fast-forwarding to the next clock event).
+   */
+  onSleep = () => {
+    /* empty by default */
+  };
+
+  /**
    * Program counter
    */
   pc: u32 = 0;
@@ -86,7 +109,10 @@ export class CPU {
   constructor(
     public progMem: Uint16Array,
     private sramBytes = 8192,
+    { dataMemoryOffset = 0, ioOffset = 32 }: { dataMemoryOffset?: number; ioOffset?: number } = {},
   ) {
+    this.dataMemoryOffset = dataMemoryOffset;
+    this.ioOffset = ioOffset;
     this.reset();
   }
 
@@ -99,13 +125,15 @@ export class CPU {
   }
 
   readData(addr: number) {
-    if (addr >= 32 && this.readHooks[addr]) {
+    addr += this.dataMemoryOffset;
+    if (this.readHooks[addr]) {
       return this.readHooks[addr](addr);
     }
     return this.data[addr];
   }
 
   writeData(addr: number, value: number, mask = 0xff) {
+    addr += this.dataMemoryOffset;
     const hook = this.writeHooks[addr];
     if (hook) {
       if (hook(value, this.data[addr], addr, mask)) {