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Implemented the Activision stack paging scheme.

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This commit is contained in:
Thomas Harte 2017-03-14 20:24:05 -04:00
parent 97a8a96593
commit 7302703039
2 changed files with 25 additions and 0 deletions
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22
Machines/Atari2600/Atari2600.cpp
View File

@ -119,6 +119,22 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
ram_read_targets_[19] = ram_write_targets_[17];
}
break;
case StaticAnalyser::Atari2600PagingModel::ActivisionStack:
if(operation == CPU6502::BusOperation::ReadOpcode) {
// if the last operation was either a JSR or an RTS, pick a new page
// based on the address now being accesses
if(last_opcode_ == 0x20 || last_opcode_ == 0x60) {
if(address & 0x2000) {
rom_pages_[0] = rom_;
} else {
rom_pages_[0] = &rom_[4096];
}
rom_pages_[1] = rom_pages_[0] + 1024;
rom_pages_[2] = rom_pages_[0] + 2048;
rom_pages_[3] = rom_pages_[0] + 3072;
}
}
break;
}
#undef AtariPager
@ -250,6 +266,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
}
if(isReadOperation(operation)) {
if(operation == CPU6502::BusOperation::ReadOpcode) last_opcode_ = returnValue;
*value = returnValue;
}
}
@ -357,6 +374,11 @@ void Machine::configure_as_target(const StaticAnalyser::Target &target) {
ram_write_targets_[17] = ram_write_targets_[16] + 128;
ram_read_targets_[18] = ram_write_targets_[16];
ram_read_targets_[19] = ram_write_targets_[17];
rom_pages_[0] = rom_;
rom_pages_[1] = rom_pages_[0] + 1024;
rom_pages_[2] = rom_pages_[0] + 2048;
rom_pages_[3] = rom_pages_[0] + 3072;
break;
}

3
Machines/Atari2600/Atari2600.hpp
View File

@ -67,6 +67,9 @@ class Machine:
std::vector<uint8_t> ram_;
uint8_t throwaway_ram_[128];
// Activision stack records
uint8_t last_opcode_;
// the RIOT and TIA
PIA mos6532_;
std::unique_ptr<TIA> tia_;