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Meanders vaguely towards a memory map.

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This commit is contained in:
Thomas Harte 2021-07-16 21:41:32 -04:00
parent d1f3b5ed80
commit f7de6f790c
1 changed files with 34 additions and 6 deletions
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40
Machines/Amiga/Amiga.cpp
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@ -29,7 +29,6 @@ class ConcreteMachine:
mc68000_(*this)
{
(void)target;
(void)rom_fetcher;
// Temporary: use a hard-coded Kickstart selection.
constexpr ROM::Name rom_name = ROM::Name::AmigaA500Kickstart13;
@ -38,7 +37,7 @@ class ConcreteMachine:
if(!request.validate(roms)) {
throw ROMMachine::Error::MissingROMs;
}
Memory::PackBigEndian16(roms.find(rom_name)->second, kickstart_);
Memory::PackBigEndian16(roms.find(rom_name)->second, kickstart_.data());
// NTSC clock rate: 2*3.579545 = 7.15909Mhz.
// PAL clock rate: 7.09379Mhz.
@ -47,16 +46,45 @@ class ConcreteMachine:
// MARK: - MC68000::BusHandler.
using Microcycle = CPU::MC68000::Microcycle;
HalfCycles perform_bus_operation(const CPU::MC68000::Microcycle &cycle, int is_supervisor) {
(void)cycle;
(void)is_supervisor;
HalfCycles perform_bus_operation(const CPU::MC68000::Microcycle &cycle, int) {
// Do nothing if no address is exposed.
if(!(cycle.operation & (Microcycle::NewAddress | Microcycle::SameAddress))) return HalfCycles(0);
// TODO: interrupt acknowledgement though?
// Grab the target address to pick a memory source.
const uint32_t address = cycle.host_endian_byte_address();
(void)address;
// Address spaces that matter:
//
// 00'0000 – 08'0000: chip RAM. [or overlayed KickStart]
// – 10'0000: extended chip ram for ECS.
// – 20'0000: auto-config space (/fast RAM).
// ...
// bf'd000 – c0'0000: 8250s.
// c0'0000 – d8'0000: pseudo-fast RAM.
// ...
// dc'0000 – dd'0000: optional real-time clock.
// df'f000 - e0'0000: custom chip registers.
// ...
// f0'0000 — : 512kb Kickstart (or possibly just an extra 512kb reserved for hypothetical 1mb Kickstart?).
// f8'0000 — : 256kb Kickstart if 2.04 or higher.
// fc'0000 – : 256kb Kickstart otherwise.
return HalfCycles(0);
}
private:
CPU::MC68000::Processor<ConcreteMachine, true> mc68000_;
std::vector<uint8_t> kickstart_;
// MARK: - Memory map.
std::array<uint8_t, 512*1024> ram_;
std::array<uint8_t, 512*1024> kickstart_;
struct MemoryRegion {
} regions_[64]; // i.e. top six bits are used as an index.
// MARK: - MachineTypes::ScanProducer.