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// SPDX-License-Identifier: MIT
// Copyright (c) Uri Shaked and contributors
import { describe, expect, it } from 'vitest';
import { CPU } from '../cpu/cpu';
import { AVRClock, clockConfig } from './clock';
// Clock Registers
const CLKPC = 0x61;
// Register bit names
const CLKPCE = 128;
describe('Clock', () => {
it('should set the prescaler when double-writing CLKPC', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 3); // Divide by 8 (2^3)
expect(clock.frequency).toEqual(2e6); // 2MHz
expect(cpu.readData(CLKPC)).toEqual(3);
});
it('should not update the prescaler if CLKPCE was not set CLKPC', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, 3); // Divide by 8 (2^3)
expect(clock.frequency).toEqual(16e6); // still 16MHz
expect(cpu.readData(CLKPC)).toEqual(0);
});
it('should not update the prescaler if more than 4 cycles passed since setting CLKPCE', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, CLKPCE);
cpu.cycles += 6;
cpu.writeData(CLKPC, 3); // Divide by 8 (2^3)
expect(clock.frequency).toEqual(16e6); // still 16MHz
expect(cpu.readData(CLKPC)).toEqual(0);
});
describe('prescaler property', () => {
it('should return the current prescaler value', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 5); // Divide by 32 (2^5)
cpu.cycles = 16e6;
expect(clock.prescaler).toEqual(32);
});
});
describe('time properties', () => {
it('should return current number of microseconds, derived from base freq + prescaler', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 2); // Divide by 4 (2^2)
cpu.cycles = 16e6;
expect(clock.timeMillis).toEqual(4000); // 4 seconds
});
it('should return current number of milliseconds, derived from base freq + prescaler', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 2); // Divide by 4 (2^2)
cpu.cycles = 16e6;
expect(clock.timeMicros).toEqual(4e6); // 4 seconds
});
it('should return current number of nanoseconds, derived from base freq + prescaler', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 2); // Divide by 4 (2^2)
cpu.cycles = 16e6;
expect(clock.timeNanos).toEqual(4e9); // 4 seconds
});
it('should correctly calculate time when changing the prescale value at runtime', () => {
const cpu = new CPU(new Uint16Array(0x1000));
const clock = new AVRClock(cpu, 16e6, clockConfig);
cpu.cycles = 16e6; // run 1 second at 16MHz
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 2); // Divide by 4 (2^2)
cpu.cycles += 2 * 4e6; // run 2 more seconds at 4MhZ
expect(clock.timeMillis).toEqual(3000); // 3 seconds in total
cpu.writeData(CLKPC, CLKPCE);
cpu.writeData(CLKPC, 1); // Divide by 2 (2^1)
cpu.cycles += 0.5 * 8e6; // run 0.5 more seconds at 8MhZ
expect(clock.timeMillis).toEqual(3500); // 3.5 seconds in total
});
});
});
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