Implement mem device for bootrom overlay

This commit is contained in:
madmaurice 2023-08-28 21:55:46 +02:00
parent e4a6b1f9b4
commit e859f8ad2c
3 changed files with 95 additions and 0 deletions

View file

@ -0,0 +1,50 @@
#include "memory/bootrom_overlay.h"
BootRom::BootRom(Mem_device* lowmem, Mem_device* highmem, Mem_device* backend)
: lowmem(lowmem), highmem(highmem), backend(backend), enabled(true)
{}
void BootRom::enable()
{
enabled = true;
}
void BootRom::disable()
{
enabled = false;
}
void BootRom::write8(u16 addr, u8 data)
{
if(enabled && (lowrange.contains(addr) || highrange.contains(addr)))
return;
backend->write8(addr, data);
}
u8 BootRom::read8(u16 addr)
{
if(enabled && lowrange.contains(addr))
return lowmem->read8(addr);
else if(enabled && highrange.contains(addr))
return highmem->read8(addr);
else
return backend->read8(addr);
}
void BootRom::write16(u16 addr, u16 data)
{
if(enabled && (lowrange.contains(addr) || highrange.contains(addr)))
return;
backend->write16(addr, data);
}
u16 BootRom::read16(u16 addr)
{
if(enabled && lowrange.contains(addr))
return lowmem->read16(addr);
else if(enabled && highrange.contains(addr))
return highmem->read16(addr);
else
return backend->read16(addr);
}

28
memory/bootrom_overlay.h Normal file
View file

@ -0,0 +1,28 @@
#pragma once
#include <memory/mem_device.h>
class BootRom : Mem_device
{
private:
Mem_device* lowmem;
Mem_device* highmem;
Mem_device* backend;
const Range lowrange(0x0000, 0x00FF);
const Range highrange(0x0200, 0x08FF);
bool enabled;
public:
BootRom(Mem_device* lowmem, Mem_device* highmem, Mem_device* backend);
void enable();
void disable();
virtual void write8(u16 addr, u8 data);
virtual u8 read8(u16 addr);
virtual void write16(u16 addr, u16 data);
virtual u16 read16(u16 addr);
}

View file

@ -2,6 +2,23 @@
#include "types.h"
class Range {
private:
u16 start;
u16 end;
public:
constexpr Range(u16 start, u16 end)
: start(start), end(end)
{};
inline
bool contains(u16 addr)
{
return addr >= start && addr <= end;
}
};
class Mem_device {
public:
virtual void write8(u16 addr, u8 data) = 0;