refactor: central interrupt handling #38

1 files changed, 76 insertions, 3 deletions

diff --git a/src/cpu/cpu.ts b/src/cpu/cpu.ts
index ed88e71..4b70efb 100644
--- a/src/cpu/cpu.ts
+++ b/src/cpu/cpu.ts
@@ -5,7 +5,8 @@
  * Copyright (C) 2019, Uri Shaked
  */
 
-import { u32, u16, u8 } from '../types';
+import { u32, u16, u8, i16 } from '../types';
+import { avrInterrupt } from './interrupt';
 
 const registerSpace = 0x100;
 
@@ -45,6 +46,15 @@ export interface CPUMemoryReadHooks {
   [key: number]: CPUMemoryReadHook;
 }
 
+export interface AVRInterruptConfig {
+  address: u8;
+  enableRegister: u16;
+  enableMask: u8;
+  flagRegister: u16;
+  flagMask: u8;
+  constant?: boolean;
+}
+
 export class CPU implements ICPU {
   readonly data: Uint8Array = new Uint8Array(this.sramBytes + registerSpace);
   readonly data16 = new Uint16Array(this.data.buffer);
@@ -52,13 +62,15 @@ export class CPU implements ICPU {
   readonly progBytes = new Uint8Array(this.progMem.buffer);
   readonly readHooks: CPUMemoryReadHooks = [];
   readonly writeHooks: CPUMemoryHooks = [];
+  private readonly pendingInterrupts: AVRInterruptConfig[] = [];
   readonly pc22Bits = this.progBytes.length > 0x20000;
 
   // This lets the Timer Compare output override GPIO pins:
   readonly gpioTimerHooks: CPUMemoryHooks = [];
 
-  pc = 0;
-  cycles = 0;
+  pc: u32 = 0;
+  cycles: u32 = 0;
+  nextInterrupt: i16 = -1;
 
   constructor(public progMem: Uint16Array, private sramBytes = 8192) {
     this.reset();
@@ -67,6 +79,8 @@ export class CPU implements ICPU {
   reset() {
     this.data.fill(0);
     this.SP = this.data.length - 1;
+    this.pendingInterrupts.splice(0, this.pendingInterrupts.length);
+    this.nextInterrupt = -1;
   }
 
   readData(addr: number) {
@@ -101,4 +115,63 @@ export class CPU implements ICPU {
   get interruptsEnabled() {
     return this.SREG & 0x80 ? true : false;
   }
+
+  private updateNextInterrupt() {
+    this.nextInterrupt = this.pendingInterrupts.findIndex((item) => !!item);
+  }
+
+  setInterruptFlag(interrupt: AVRInterruptConfig) {
+    const { flagRegister, flagMask, enableRegister, enableMask } = interrupt;
+    if (interrupt.constant) {
+      this.data[flagRegister] &= ~flagMask;
+    } else {
+      this.data[flagRegister] |= flagMask;
+    }
+    if (this.data[enableRegister] & enableMask) {
+      this.queueInterrupt(interrupt);
+    }
+  }
+
+  updateInterruptEnable(interrupt: AVRInterruptConfig, registerValue: u8) {
+    const { enableMask, flagRegister, flagMask } = interrupt;
+    if (registerValue & enableMask) {
+      if (this.data[flagRegister] & flagMask) {
+        this.queueInterrupt(interrupt);
+      }
+    } else {
+      this.clearInterrupt(interrupt, false);
+    }
+  }
+
+  queueInterrupt(interrupt: AVRInterruptConfig) {
+    this.pendingInterrupts[interrupt.address] = interrupt;
+    this.updateNextInterrupt();
+  }
+
+  clearInterrupt({ address, flagRegister, flagMask }: AVRInterruptConfig, clearFlag = true) {
+    delete this.pendingInterrupts[address];
+    if (clearFlag) {
+      this.data[flagRegister] &= ~flagMask;
+    }
+    this.updateNextInterrupt();
+  }
+
+  clearInterruptByFlag(interrupt: AVRInterruptConfig, registerValue: number) {
+    const { flagRegister, flagMask } = interrupt;
+    if (registerValue & flagMask) {
+      this.data[flagRegister] &= ~flagMask;
+      this.clearInterrupt(interrupt);
+    }
+  }
+
+  tick() {
+    if (this.interruptsEnabled && this.nextInterrupt >= 0) {
+      const interrupt = this.pendingInterrupts[this.nextInterrupt];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      avrInterrupt(this, interrupt.address);
+      if (!interrupt.constant) {
+        this.clearInterrupt(interrupt);
+      }
+    }
+  }
 }