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/**
* AVR 8 CPU data structures
* Part of AVR8js
*
* Copyright (C) 2019, Uri Shaked
*/
import { u32, u16, u8, i16 } from '../types';
import { avrInterrupt } from './interrupt';
const registerSpace = 0x100;
// eslint-disable-next-line @typescript-eslint/interface-name-prefix
export interface ICPU {
readonly data: Uint8Array;
readonly dataView: DataView;
readonly progMem: Uint16Array;
readonly progBytes: Uint8Array;
/**
* Whether the program counter (PC) can address 22 bits (the default is 16)
*/
readonly pc22Bits: boolean;
/**
* Program counter
*/
pc: u32;
/**
* Clock cycle counter
*/
cycles: number;
readData(addr: u16): u8;
writeData(addr: u16, value: u8): void;
}
export type CPUMemoryHook = (value: u8, oldValue: u8, addr: u16) => boolean | void;
export interface CPUMemoryHooks {
[key: number]: CPUMemoryHook;
}
export type CPUMemoryReadHook = (addr: u16) => u8;
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);
readonly dataView = new DataView(this.data.buffer);
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: u32 = 0;
cycles: u32 = 0;
nextInterrupt: i16 = -1;
constructor(public progMem: Uint16Array, private sramBytes = 8192) {
this.reset();
}
reset() {
this.data.fill(0);
this.SP = this.data.length - 1;
this.pendingInterrupts.splice(0, this.pendingInterrupts.length);
this.nextInterrupt = -1;
}
readData(addr: number) {
if (addr >= 32 && this.readHooks[addr]) {
return this.readHooks[addr](addr);
}
return this.data[addr];
}
writeData(addr: number, value: number) {
const hook = this.writeHooks[addr];
if (hook) {
if (hook(value, this.data[addr], addr)) {
return;
}
}
this.data[addr] = value;
}
get SP() {
return this.dataView.getUint16(93, true);
}
set SP(value: number) {
this.dataView.setUint16(93, value, true);
}
get SREG() {
return this.data[95];
}
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);
}
}
}
}
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