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Add address rotation for applicable modes.

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This commit is contained in:
Thomas Harte 2023-01-21 22:33:26 -05:00
parent c9734df65c
commit 696ec12516
2 changed files with 20 additions and 8 deletions
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2
Components/9918/Implementation/9918.cpp
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@ -818,7 +818,7 @@ void Base<personality>::commit_register(int reg, uint8_t value) {
case 45:
LOG("TODO: Yamaha VRAM bank selection addressing and command arguments; " << PADHEX(2) << +value);
// b6: 0 = video RAM; 1 = expandion RAM.
// b6: 0 = video RAM; 1 = expansion RAM.
// b5: MXD (???)
// b4: MXS
// b3: DIY

26
Components/9918/Implementation/9918Base.hpp
View File

@ -391,12 +391,25 @@ template <Personality personality> struct Base: public Storage<personality> {
void do_external_slot(int access_column) {
// Don't do anything if the required time for the access to become executable
// has yet to pass.
if(access_column < minimum_access_column_) {
if(queued_access_ == MemoryAccess::None || access_column < minimum_access_column_) {
return;
}
size_t address = ram_pointer_;
++ram_pointer_;
if constexpr (is_yamaha_vdp(personality)) {
const ScreenMode mode = current_screen_mode();
if(mode == ScreenMode::YamahaGraphics6 || mode == ScreenMode::YamahaGraphics7) {
// Rotate address one to the right as the hardware accesses
// the underlying banks of memory alternately but presents
// them as if linear.
address = (address >> 1) | (address << 16);
}
}
switch(queued_access_) {
default: return;
default: break;
case MemoryAccess::Write:
if constexpr (is_sega_vdp(personality)) {
@ -405,7 +418,7 @@ template <Personality personality> struct Base: public Storage<personality> {
// scale; cf. https://www.retrorgb.com/sega-master-system-non-linear-blue-channel-findings.html
constexpr uint8_t rg_scale[] = {0, 85, 170, 255};
constexpr uint8_t b_scale[] = {0, 104, 170, 255};
Storage<personality>::colour_ram_[ram_pointer_ & 0x1f] = palette_pack(
Storage<personality>::colour_ram_[address & 0x1f] = palette_pack(
rg_scale[(read_ahead_buffer_ >> 0) & 3],
rg_scale[(read_ahead_buffer_ >> 2) & 3],
b_scale[(read_ahead_buffer_ >> 4) & 3]
@ -427,17 +440,16 @@ template <Personality personality> struct Base: public Storage<personality> {
dot.location.row += dot.location.column / 342;
dot.location.column %= 342;
dot.value = Storage<personality>::colour_ram_[ram_pointer_ & 0x1f];
dot.value = Storage<personality>::colour_ram_[address & 0x1f];
break;
}
}
ram_[ram_pointer_ & memory_mask(personality)] = read_ahead_buffer_;
ram_[address & memory_mask(personality)] = read_ahead_buffer_;
break;
case MemoryAccess::Read:
read_ahead_buffer_ = ram_[ram_pointer_ & memory_mask(personality)];
read_ahead_buffer_ = ram_[address & memory_mask(personality)];
break;
}
++ram_pointer_;
queued_access_ = MemoryAccess::None;
}