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Switch DDFSTART/STOP state machine.

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This commit is contained in:
Thomas Harte 2022-03-17 19:39:24 -04:00
parent 88c7a6d053
commit 88767e402c
2 changed files with 27 additions and 15 deletions
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34
Machines/Amiga/Chipset.cpp
View File

@ -146,7 +146,6 @@ void Chipset::output_pixels(int cycles_until_sync) {
const uint32_t playfield = bitplane_pixels_.get(is_high_res_);
// Output playfield pixels, if a buffer was allocated.
// TODO: HAM.
if(pixels_) {
if(hold_and_modify_) {
apply_ham(uint8_t(playfield >> 16));
@ -507,18 +506,28 @@ template <int cycle, bool stop_if_cpu> bool Chipset::perform_cycle() {
//
// Top priority: bitplane collection.
// TODO: mask off fetch_window_'s lower bits. (Dependant on high/low-res?)
// Also: fetch_stop_ and that + 12/8 is the best I can discern from the Hardware Reference,
// but very obviously isn't how the actual hardware works. Explore on that.
fetch_horizontal_ |= cycle == fetch_window_[0];
if(cycle == fetch_window_[1]) fetch_stop_ = cycle + (is_high_res_ ? 12 : 8);
fetch_horizontal_ &= cycle != fetch_stop_;
if((dma_control_ & BitplaneFlag) == BitplaneFlag) {
if(fetch_vertical_ && fetch_horizontal_ && bitplanes_.advance_dma(cycle)) {
if(cycle == fetch_window_[0]) {
// printf("Enabled: %d; ", cycle);
horizontal_fetch_ = HorizontalFetch::Enabled;
horizontal_offset_ = cycle;
}
if(horizontal_fetch_ != HorizontalFetch::Disabled) {
if(!((cycle - horizontal_offset_)&7)) {
if(horizontal_fetch_ == HorizontalFetch::StopRequested) {
// printf("Disabled: %d\n", cycle);
horizontal_fetch_ = HorizontalFetch::Disabled;
}
}
if(horizontal_fetch_ != HorizontalFetch::Disabled && (dma_control_ & BitplaneFlag) == BitplaneFlag && fetch_vertical_ && bitplanes_.advance_dma(cycle - horizontal_offset_)) {
did_fetch_ = true;
return false;
}
}
if(cycle == fetch_window_[1]) {
// printf("Disabling: %d; ", cycle);
horizontal_fetch_ = HorizontalFetch::StopRequested;
}
// Contradictory snippets from the Hardware Reference manual:
//
@ -712,8 +721,7 @@ template <bool stop_on_cpu> Chipset::Changes Chipset::run(HalfCycles length) {
previous_bitplanes_.clear();
}
did_fetch_ = false;
fetch_horizontal_ = false;
fetch_stop_ = 0xffff;
horizontal_fetch_ = HorizontalFetch::Disabled;
if(y_ == short_field_height_ + is_long_field_) {
++vsyncs;
@ -921,7 +929,7 @@ void Chipset::write(uint32_t address, uint16_t value, bool allow_conversion) {
if(fetch_window_[0] != value) {
LOG("Fetch window start set to " << std::dec << value);
}
fetch_window_[0] = value;
fetch_window_[0] = value & 0xfe;
break;
case 0x094: // DDFSTOP
// TODO: something in my interpretation of ddfstart and ddfstop
@ -929,7 +937,7 @@ void Chipset::write(uint32_t address, uint16_t value, bool allow_conversion) {
if(fetch_window_[1] != value) {
LOG("Fetch window stop set to " << std::dec << fetch_window_[1]);
}
fetch_window_[1] = value;
fetch_window_[1] = value & 0xfe;
break;
// Bitplanes.

8
Machines/Amiga/Chipset.hpp
View File

@ -166,10 +166,14 @@ class Chipset: private ClockingHint::Observer {
uint16_t fetch_window_[2] = {0, 0};
// Ephemeral bitplane collection state.
bool fetch_vertical_ = false, fetch_horizontal_ = false;
bool fetch_vertical_ = false;
bool display_horizontal_ = false;
bool did_fetch_ = false;
uint16_t fetch_stop_ = 0xffff;
int horizontal_offset_ = 0;
enum HorizontalFetch {
Disabled, Enabled, StopRequested
} horizontal_fetch_ = HorizontalFetch::Disabled;
// Output state.
uint16_t border_colour_ = 0;