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Makes some attempt to implement paging.

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This causes several of the 32kb games to be recognised by the BIOS and permitted to start, so it really really may be time to stop deferring work on the VDP.
This commit is contained in:
Thomas Harte 2018-09-24 21:34:42 -04:00
parent 7515fa8a98
commit 2e4c4c3e91
1 changed files with 46 additions and 13 deletions
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59
Machines/MasterSystem/MasterSystem.cpp
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@ -22,6 +22,8 @@
#include "../../Analyser/Static/Sega/Target.hpp"
#include <algorithm>
namespace {
const int sn76489_divider = 2;
}
@ -91,16 +93,17 @@ class ConcreteMachine:
joysticks_.emplace_back(new Joystick);
// Clear the memory map.
for(auto &pointer: read_pointers_) {
pointer = nullptr;
}
for(auto &pointer: write_pointers_) {
pointer = nullptr;
}
map(read_pointers_, nullptr, 0x10000, 0);
map(write_pointers_, nullptr, 0x10000, 0);
// Take a copy of the cartridge and place it into memory.
cartridge_ = target.media.cartridges[0]->get_segments()[0].data;
map(read_pointers_, cartridge_.data(), static_cast<int>(cartridge_.size()), 0x0000, 0xc000);
if(cartridge_.size() < 48*1024) {
std::size_t new_space = 48*1024 - cartridge_.size();
cartridge_.resize(48*1024);
memset(&cartridge_[48*1024 - new_space], 0xff, new_space);
}
page_cartridge();
// Establish the BIOS (if relevant) and RAM.
if(target.model == Analyser::Static::Sega::Target::Model::MasterSystem) {
@ -159,7 +162,11 @@ class ConcreteMachine:
break;
case CPU::Z80::PartialMachineCycle::Write:
if(write_pointers_[address >> 10]) write_pointers_[address >> 10][address & 1023] = *cycle.value;
if(address >= 0xfffd && cartridge_.size() > 48*1024) {
paging_registers_[address - 0xfffd] = *cycle.value;
page_cartridge();
}
else if(write_pointers_[address >> 10]) write_pointers_[address >> 10][address & 1023] = *cycle.value;
break;
case CPU::Z80::PartialMachineCycle::Input:
@ -201,7 +208,21 @@ class ConcreteMachine:
case CPU::Z80::PartialMachineCycle::Output:
switch(address & 0xc1) {
case 0x00:
printf("TODO: [output] memory control\n");
if(model_ == Analyser::Static::Sega::Target::Model::MasterSystem) {
// TODO: Obey the RAM enable.
// Either install the cartridge or don't.
if(!((*cycle.value) & 0x40)) {
page_cartridge();
} else {
map(read_pointers_, nullptr, 0xc000, 0x0000);
}
// Throw the BIOS on top if it isn't disabled.
if(!((*cycle.value) & 0x08)) {
map(read_pointers_, bios_, 8*1024, 0);
}
}
break;
case 0x01:
printf("TODO: [output] I/O port control\n");
@ -286,10 +307,22 @@ class ConcreteMachine:
// The memory map has a 1kb granularity; this is determined by the SG1000's 1kb of RAM.
const uint8_t *read_pointers_[64];
uint8_t *write_pointers_[64];
template <typename T> void map(T **target, uint8_t *source, int size, int start_address, int end_address = -1) {
if(end_address == -1) end_address = start_address + size;
for(int address = start_address; address < end_address; address += 1024) {
target[address >> 10] = &source[(address - start_address) & (size - 1)];
template <typename T> void map(T **target, uint8_t *source, size_t size, size_t start_address, size_t end_address = 0) {
if(!end_address) end_address = start_address + size;
for(auto address = start_address; address < end_address; address += 1024) {
target[address >> 10] = source ? &source[(address - start_address) & (size - 1)] : nullptr;
}
}
uint8_t paging_registers_[3] = {0, 1, 2};
void page_cartridge() {
for(size_t c = 0; c < 3; ++c) {
const size_t start_addr = (paging_registers_[c] * 0x4000) % cartridge_.size();
map(
read_pointers_,
cartridge_.data() + start_addr,
std::min(static_cast<size_t>(0x4000), cartridge_.size() - start_addr),
c * 0x4000);
}
}
};