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Merge pull request #109 from TomHarte/CBSRamPlus

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Adds emulation of the CBS RAM Plus paging scheme.
This commit is contained in:
Thomas Harte 2017-03-14 17:26:09 -04:00 committed by GitHub
commit 4a528b9ecb
1 changed files with 24 additions and 20 deletions
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44
Machines/Atari2600/Atari2600.cpp
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@ -68,30 +68,25 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
if(operation != CPU6502::BusOperation::Ready) {
uint16_t masked_address = address & 0x1fff;
#define AtariPager(start, end) \
if(masked_address >= start && masked_address <= end) { \
uint8_t *base_ptr = &rom_[(masked_address - start) * 4096];\
if(base_ptr != rom_pages_[0]) {\
rom_pages_[0] = base_ptr;\
rom_pages_[1] = base_ptr + 1024;\
rom_pages_[2] = base_ptr + 2048;\
rom_pages_[3] = base_ptr + 3072;\
}\
}
// check for potential paging
switch(paging_model_) {
default:
// check for an Atari paging access
if(rom_size_ > 4096 && ((address & 0x1f00) == 0x1f00)) {
uint8_t *base_ptr = rom_pages_[0];
uint8_t first_paging_register = (uint8_t)(0xf8 - (rom_size_ >> 14)*2);
const uint8_t paging_register = address&0xff;
if(paging_register >= first_paging_register) {
const uint16_t selected_page = paging_register - first_paging_register;
if(selected_page * 4096 < rom_size_) {
base_ptr = &rom_[selected_page * 4096];
}
}
if(base_ptr != rom_pages_[0]) {
rom_pages_[0] = base_ptr;
rom_pages_[1] = base_ptr + 1024;
rom_pages_[2] = base_ptr + 2048;
rom_pages_[3] = base_ptr + 3072;
}
}
break;
case StaticAnalyser::Atari2600PagingModel::Atari8k: AtariPager(0x1ff8, 0x1ff9); break;
case StaticAnalyser::Atari2600PagingModel::CBSRamPlus: AtariPager(0x1ff8, 0x1ffa); break;
case StaticAnalyser::Atari2600PagingModel::Atari16k: AtariPager(0x1ff6, 0x1ff9); break;
case StaticAnalyser::Atari2600PagingModel::Atari32k: AtariPager(0x1ff4, 0x1ffb); break;
case StaticAnalyser::Atari2600PagingModel::ParkerBros:
if(masked_address >= 0x1fe0 && masked_address < 0x1ff8) {
int slot = (masked_address >> 3) & 3;
@ -101,6 +96,8 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
break;
}
#undef AtariPager
// check for a ROM read
if(address&0x1000)
{
@ -319,6 +316,13 @@ void Machine::configure_as_target(const StaticAnalyser::Target &target)
}
break;
case StaticAnalyser::Atari2600PagingModel::CBSRamPlus:
ram_.resize(256);
has_ram_ = true;
ram_write_start_ = 0x1000;
ram_read_start_ = 0x1100;
break;
case StaticAnalyser::Atari2600PagingModel::CommaVid:
ram_.resize(1024);
has_ram_ = true;