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Takes a shot at the vertical stuff of sprite DMA.

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This commit is contained in:
Thomas Harte 2021-10-22 14:32:59 -07:00
parent b489ba3d0d
commit 040ac93042
2 changed files with 68 additions and 4 deletions
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57
Machines/Amiga/Chipset.cpp
View File

@ -269,7 +269,7 @@ template <int cycle, bool stop_if_cpu> bool Chipset::perform_cycle() {
if constexpr(cycle >= 0x15 && cycle < 0x35) {
if((dma_control_ & SpritesFlag) == SpritesFlag) {
constexpr auto sprite_id = (cycle - 0x15) >> 2;
if(sprites_[sprite_id].advance(sprite_id)) {
if(sprites_[sprite_id].advance(y_)) {
return false;
}
}
@ -404,6 +404,11 @@ template <bool stop_on_cpu> Chipset::Changes Chipset::run(HalfCycles length) {
// TODO: the manual is vague on when this happens. Try to find out.
copper_.reload<0>();
// TODO: is this really how sprite DMA proceeds?
for(int c = 0; c < 8; c++) {
sprites_[c].reset_dma();
}
}
}
assert(line_cycle_ < line_length_ * 4);
@ -936,10 +941,58 @@ void Chipset::Sprite::set_image_data(int slot, uint16_t value) {
active_ |= slot == 0;
}
bool Chipset::Sprite::advance([[maybe_unused]] int sprite_id) {
bool Chipset::Sprite::advance(int y) {
switch(dma_state_) {
// i.e. stopped.
default: return false;
// FetchStart: fetch the first control word and proceed to the second.
case DMAState::FetchStart:
set_start_position(ram_[pointer_[0]]);
++pointer_[0];
dma_state_ = DMAState::FetchStopAndControl;
return true;
// FetchStopAndControl: fetch second control word and wait for V start.
case DMAState::FetchStopAndControl:
set_stop_and_control(ram_[pointer_[0]]);
++pointer_[0];
dma_state_ = DMAState::WaitingForStart;
return true;
// WaitingForStart: repeat until V start is found.
case DMAState::WaitingForStart:
if(y != v_start_) {
return false;
}
[[fallthrough]];
// FetchData1: if v end is reached, stop DMA. Otherwise fetch a word
// and proceed to FetchData0.
case DMAState::FetchData1:
if(y == v_stop_) {
dma_state_ = DMAState::Stopped;
return false;
}
set_image_data(1, ram_[pointer_[0]]);
++pointer_[0];
dma_state_ = DMAState::FetchData0;
return true;
// FetchData0: fetch a word and proceed back to FetchData1.
case DMAState::FetchData0:
set_image_data(0, ram_[pointer_[0]]);
++pointer_[0];
dma_state_ = DMAState::FetchData1;
return true;
}
return false;
}
void Chipset::Sprite::reset_dma() {
dma_state_ = DMAState::FetchStart;
}
// MARK: - Disk.
void Chipset::DiskDMA::enqueue(uint16_t value, bool matches_sync) {

15
Machines/Amiga/Chipset.hpp
View File

@ -132,12 +132,23 @@ class Chipset: private ClockingHint::Observer {
void set_stop_and_control(uint16_t value);
void set_image_data(int slot, uint16_t value);
bool advance(int sprite_id);
bool advance(int y);
void reset_dma();
private:
uint16_t v_start_ = 0, h_start_ = 0, v_stop_ = 0;
uint16_t data_[2]{};
bool active_ = false, attached_ = false;
bool attached_ = false;
bool active_ = false;
enum class DMAState {
FetchStart,
FetchStopAndControl,
WaitingForStart,
FetchData1,
FetchData0,
Stopped
} dma_state_ = DMAState::FetchStart;
} sprites_[8];
// MARK: - Raster position and state.