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Limits regions accessible to the 6560 to those built into the machine.

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This commit is contained in:
Thomas Harte 2018-04-11 21:35:23 -04:00
parent 8d4d5d1f46
commit 3ad0b31db8
1 changed files with 16 additions and 5 deletions
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21
Machines/Commodore/Vic-20/Vic20.cpp
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@ -34,6 +34,7 @@
#include "../../../Analyser/Static/Commodore/Target.hpp"
#include <algorithm>
#include <array>
#include <cstdint>
namespace Commodore {
@ -489,11 +490,21 @@ class ConcreteMachine:
// also push memory resources into the 6560 video memory map; the 6560 has only a
// 14-bit address bus and the top bit is invested and used as bit 15 for the main
// memory bus.
for(int addr = 0; addr < 0x4000; addr += 0x400) {
int source_address = (addr & 0x1fff) | (((addr & 0x2000) << 2) ^ 0x8000);
if(processor_read_memory_map_[source_address >> 10]) {
write_to_map(mos6560_->video_memory_map, &ram_[source_address], static_cast<uint16_t>(addr), 0x400);
// memory bus. It can access only internal memory, so the first 1kb, then the 4kb from 0x1000.
struct range {
const std::size_t start, end;
range(std::size_t start, std::size_t end) : start(start), end(end) {}
};
const std::array<range, 2> video_ranges = {{
range(0x0000, 0x0400),
range(0x1000, 0x2000),
}};
for(auto &video_range : video_ranges) {
for(auto addr = video_range.start; addr < video_range.end; addr += 0x400) {
auto destination_address = (addr & 0x1fff) | (((addr & 0x8000) >> 2) ^ 0x2000);
if(processor_read_memory_map_[addr >> 10]) {
write_to_map(mos6560_->video_memory_map, &ram_[addr], static_cast<uint16_t>(destination_address), 0x400);
}
}
}
mos6560_->colour_memory = colour_ram_;