EightBit/MC6850/src/MC6850.cpp

<EFBFBD><EFBFBD>#include "pch.h"
#include "MC6850.h"

#include <cassert>

bool EightBit::mc6850::selected() {
	return
			(CS0() == PinLevel::High)
		&&	(CS1() == PinLevel::High)
		&&	(CS2() == PinLevel::Low);
}

void EightBit::mc6850::reset() {
	if (!m_powered)
		IRQ() = RTS() = PinLevel::High;
	status() = 0;
	m_powered = true;
}

void EightBit::mc6850::step(int cycles) {
	for (int i = 0; i < cycles; ++i)
		step();
}

void EightBit::mc6850::step() {

	if (!(powered() && selected()))
		return;

	Accessing.fire(EventArgs::empty());

	const bool writing = RW() == PinLevel::Low;
	const bool reading = !writing;

	const bool registers = RS() == PinLevel::Low;
	const bool transferring = !registers;

	if (registers) {
		if (writing) {
			m_counterDivide = DATA() && (CR0 | CR1);
			const bool masterReset = m_counterDivide == 0b11;
			if (masterReset) {
				reset();
			} else {
				m_wordConfiguration = (DATA() && (CR2 | CR3 | CR4)) >> 2;
				m_transmitterControl = (DATA() && (CR5 | CR6)) >> 5;
				m_receiveControl = (DATA() && CR7) >> 7;
			}
		} else {
			DATA() = status();
		}
	} else {
		IRQ() = PinLevel::High;
		if (writing)
			fillTDR();
		else
			drainRDR();
	}

	Accessed.fire(EventArgs::empty());
}

void EightBit::mc6850::fillRDR() {
	Receiving.fire(EventArgs::empty());
	RDR() = DATA();
	Processor::setFlag(status(), RDRF, true);
}

void EightBit::mc6850::drainRDR() {
	Processor::setFlag(status(), RDRF, false);
	DATA() = RDR();
	Received.fire(EventArgs::empty());
}

void EightBit::mc6850::fillTDR() {
	Transmitting.fire(EventArgs::empty());
	TDR() = DATA();
}

void EightBit::mc6850::drainTDR() {
	DATA() = TDR();
	Transmitted.fire(EventArgs::empty());
}