mirror of
https://github.com/TomHarte/CLK.git
synced 2024-08-16 16:28:59 +00:00
256 lines
5.5 KiB
C++
256 lines
5.5 KiB
C++
//
|
||
// Electron.cpp
|
||
// Clock Signal
|
||
//
|
||
// Created by Thomas Harte on 03/01/2016.
|
||
// Copyright © 2016 Thomas Harte. All rights reserved.
|
||
//
|
||
|
||
#include "Electron.hpp"
|
||
|
||
#include <algorithm>
|
||
|
||
using namespace Electron;
|
||
|
||
static const int cycles_per_line = 128;
|
||
static const int cycles_per_frame = 312*cycles_per_line;
|
||
static const int crt_cycles_multiplier = 8;
|
||
static const int crt_cycles_per_line = crt_cycles_multiplier * cycles_per_line;
|
||
|
||
Machine::Machine() :
|
||
_interruptControl(0),
|
||
_frameCycles(0),
|
||
_outputPosition(0)
|
||
{
|
||
_crt = new Outputs::CRT(crt_cycles_per_line, 312, 1, 1);
|
||
_interruptStatus = 0x02;
|
||
setup6502();
|
||
}
|
||
|
||
Machine::~Machine()
|
||
{
|
||
}
|
||
|
||
unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value)
|
||
{
|
||
unsigned int cycles = 1;
|
||
|
||
if(address < 32768)
|
||
{
|
||
if(isReadOperation(operation))
|
||
{
|
||
*value = _ram[address];
|
||
}
|
||
else
|
||
{
|
||
_ram[address] = *value;
|
||
|
||
// TODO: range check on address; a lot of the time the machine will be running code outside of
|
||
// the screen area, meaning that no update is required.
|
||
// if (address
|
||
update_display();
|
||
}
|
||
|
||
// TODO: RAM timing for Modes 0–3
|
||
cycles += (_frameCycles&1)^1;
|
||
}
|
||
else
|
||
{
|
||
if(address > 49152)
|
||
{
|
||
if((address & 0xff00) == 0xfe00)
|
||
{
|
||
// printf("%c: %02x: ", isReadOperation(operation) ? 'r' : 'w', *value);
|
||
|
||
switch(address&0xf)
|
||
{
|
||
case 0x0:
|
||
if(isReadOperation(operation))
|
||
{
|
||
*value = _interruptStatus;
|
||
_interruptStatus &= ~0x02;
|
||
}
|
||
else
|
||
{
|
||
_interruptControl = *value;
|
||
evaluate_interrupts();
|
||
}
|
||
break;
|
||
case 0x1:
|
||
break;
|
||
case 0x2:
|
||
_startScreenAddress = (_startScreenAddress & 0xff00) | ((*value) & 0xe0);
|
||
break;
|
||
case 0x3:
|
||
_startScreenAddress = (_startScreenAddress & 0x00ff) | (uint16_t)(((*value) & 0x3f) << 8);
|
||
break;
|
||
case 0x4:
|
||
printf("Cassette\n");
|
||
break;
|
||
case 0x5:
|
||
if(!isReadOperation(operation))
|
||
{
|
||
uint8_t nextROM = (*value)&0xf;
|
||
if((_activeRom&0x12) != 0x8 || nextROM >= 8)
|
||
{
|
||
_activeRom = (Electron::ROMSlot)nextROM;
|
||
}
|
||
|
||
if( (*value)&0x10 ) _interruptStatus &= ~InterruptDisplayEnd;
|
||
if( (*value)&0x20 ) _interruptStatus &= InterruptRealTimeClock;
|
||
if( (*value)&0x40 ) _interruptStatus &= InterruptHighToneDetect;
|
||
evaluate_interrupts();
|
||
|
||
// TODO: NMI (?)
|
||
}
|
||
break;
|
||
case 0x6:
|
||
printf("Counter\n");
|
||
break;
|
||
case 0x7:
|
||
printf("Misc. control\n");
|
||
break;
|
||
default:
|
||
update_display();
|
||
// printf("Palette\n");
|
||
break;
|
||
}
|
||
}
|
||
else
|
||
{
|
||
if(isReadOperation(operation))
|
||
*value = _os[address - 49152];
|
||
}
|
||
}
|
||
else
|
||
{
|
||
if(isReadOperation(operation))
|
||
{
|
||
switch(_activeRom)
|
||
{
|
||
case ROMSlotBASIC:
|
||
case ROMSlotBASIC+1:
|
||
*value = _basic[address - 32768];
|
||
break;
|
||
case ROMSlotKeyboard:
|
||
case ROMSlotKeyboard+1:
|
||
*value = 0;
|
||
break;
|
||
default: break;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
_frameCycles += cycles;
|
||
if(_frameCycles == cycles_per_frame)
|
||
{
|
||
update_display();
|
||
_frameCycles = 0;
|
||
}
|
||
if(_frameCycles == 128*128) signal_interrupt(InterruptRealTimeClock);
|
||
if(_frameCycles == 284*128) signal_interrupt(InterruptDisplayEnd);
|
||
|
||
return cycles;
|
||
}
|
||
|
||
void Machine::set_rom(ROMSlot slot, size_t length, const uint8_t *data)
|
||
{
|
||
uint8_t *target = nullptr;
|
||
switch(slot)
|
||
{
|
||
case ROMSlotBASIC: target = _basic; break;
|
||
case ROMSlotOS: target = _os; break;
|
||
default: return;
|
||
}
|
||
|
||
memcpy(target, data, std::min((size_t)16384, length));
|
||
}
|
||
|
||
inline void Machine::signal_interrupt(Electron::Interrupt interrupt)
|
||
{
|
||
_interruptStatus |= (interrupt << 2);
|
||
evaluate_interrupts();
|
||
}
|
||
|
||
inline void Machine::evaluate_interrupts()
|
||
{
|
||
if(_interruptStatus & _interruptControl)
|
||
{
|
||
_interruptStatus |= 1;
|
||
}
|
||
set_irq_line(_interruptStatus & 1);
|
||
}
|
||
|
||
inline void Machine::update_display()
|
||
{
|
||
const int end_of_hsync = 3 * cycles_per_line;
|
||
|
||
if(_frameCycles >= end_of_hsync)
|
||
{
|
||
// assert sync for the first three lines of the display
|
||
if(_outputPosition < end_of_hsync)
|
||
{
|
||
_crt->output_sync(end_of_hsync * crt_cycles_multiplier);
|
||
_outputPosition = end_of_hsync;
|
||
}
|
||
|
||
while(_outputPosition >= end_of_hsync && _outputPosition < _frameCycles)
|
||
{
|
||
const int current_line = _outputPosition >> 7;
|
||
const int line_position = _outputPosition & 127;
|
||
|
||
// all lines then start with 9 cycles of sync
|
||
if(!line_position)
|
||
{
|
||
_crt->output_sync(9 * crt_cycles_multiplier);
|
||
_outputPosition += 9;
|
||
}
|
||
else
|
||
{
|
||
// on lines prior to 28 or after or equal to 284, or on a line that is equal to 8 or 9 modulo 10 in a line-spaced mode,
|
||
// the line is then definitely blank.
|
||
if(current_line < 28 || current_line >= 284)
|
||
{
|
||
if(line_position == 9)
|
||
{
|
||
_crt->output_blank(119 * crt_cycles_multiplier);
|
||
_outputPosition = (_outputPosition + 119) % cycles_per_frame;;
|
||
}
|
||
}
|
||
else
|
||
{
|
||
// there are then 15 cycles of blank, 80 cycles of pixels, and 24 further cycles of blank
|
||
if(line_position == 9)
|
||
{
|
||
_crt->output_blank(15 * crt_cycles_multiplier);
|
||
_outputPosition += 15;
|
||
_crt->output_data(80 * crt_cycles_multiplier);
|
||
}
|
||
|
||
if(line_position >= 24 && line_position < 104)
|
||
{
|
||
// TODO: actually output some pixels, why not?
|
||
_outputPosition++;
|
||
}
|
||
|
||
if(line_position == 104)
|
||
{
|
||
_crt->output_blank(24 * crt_cycles_multiplier);
|
||
_outputPosition += 24;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
const char *Machine::get_signal_decoder()
|
||
{
|
||
return
|
||
"vec4 sample(vec2 coordinate)\n"
|
||
"{\n"
|
||
"return vec4(1.0, 1.0, 0.0, 1.0);\n"
|
||
"}";
|
||
}
|