PET/petio.cpp at master · jscrane/PET · GitHub

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#include <stdint.h>

#include <machine.h>
#include <memory.h>
#include <serialio.h>
#include <filer.h>
#include <pia.h>
#include <via.h>
#include <debugging.h>

#include "petio.h"
#include "sound.h"

// see http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/PET-Interfaces.txt
// and http://www.6502.org/users/andre/petindex/progmod.html

// device offsets (base is 0xe800)
#define PIA1_OFFSET	0x0010
#define PIA2_OFFSET	0x0020
#define VIA_OFFSET	0x0040

// via port-b
#define VIDEO_RETRACE	0x20

// 1ms internal clock tick
#define TICK_PERIOD	1000

sound sound;

petio::petio(filer &files): files(files), _ticks(0), _timer(-1) {
	put(pia1, PIA1_OFFSET);
	put(pia2, PIA2_OFFSET);
	put(via, VIA_OFFSET);
}

void petio::reset() {

	sound.reset();
	pia1.reset();
	pia2.reset();
	via.reset();

	via.register_portb_input_handler([this]() { return _ticks >= 14? VIDEO_RETRACE: 0; });

	if (_timer >= 0)
		_machine->cancel_timer(_timer);
	_timer = _machine->interval_timer(TICK_PERIOD, [this]() { tick(); });
}

// 60Hz is approx 16.67ms. Using 17 ticks @ 1ms = 58.8Hz.
// 0-13 = Active Display (14ms)
// 14-16 = Retrace (3ms)
void petio::tick() {

	pia1.write_cb1(_ticks < 14);

	if (++_ticks == 17)
		_ticks = 0;
}

void petio::operator=(uint8_t r) {

	Devices::operator=(r);

	switch (_acc - VIA_OFFSET) {
	case 0x08:
		sound.frequency(r);
		break;
	case 0x0a:
		sound.octave(r);
		break;
	case 0x0b:
		sound.on_off((r & VIA::ACR_SHIFT_MASK) == VIA::ACR_SO_T2_RATE);
		break;
	}
}

bool petio::load_prg() {

	extern Memory memory;

	if (!files.more())
		return false;

	uint8_t lo = files.read();
	uint8_t hi = files.read();
	Memory::address a = lo + (hi << 8);
	while (files.more())
		memory[a++] = files.read();

	// based on mem_get/set_basic_text() from vice/petmem.c
	memory[0xc7] = memory[0x28];
	memory[0xc8] = memory[0x29];

	lo = (uint8_t)(a & 0xff);
	memory[0x2a] = lo;
	memory[0x2c] = lo;
	memory[0x2e] = lo;
	memory[0xc9] = lo;

	hi = (uint8_t)(a >> 8);
	memory[0x2b] = hi;
	memory[0x2d] = hi;
	memory[0x2f] = hi;
	memory[0xca] = hi;

	return true;
}