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Introduces filtering of the CRTC's vsync signal into the gate array.
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@ -147,7 +147,8 @@ class CRTCBusHandler {
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interrupt_timer_(interrupt_timer),
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pixel_divider_(1),
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mode_(2),
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next_mode_(2) {
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next_mode_(2),
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cycles_into_hsync_(0) {
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build_mode_tables();
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}
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@ -156,8 +157,19 @@ class CRTCBusHandler {
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to produce based on the current palette and mode.
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*/
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inline void perform_bus_cycle(const Motorola::CRTC::BusState &state) {
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// The gate array waits 2µs to react to the CRTC's vsync signal, and then
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// caps output at 4µs. Since the clock rate is 1Mhz, that's 2 and 4 cycles,
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// respectively.
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if(state.hsync) {
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cycles_into_hsync_++;
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} else {
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cycles_into_hsync_ = 0;
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}
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bool is_hsync = (cycles_into_hsync_ >= 2 && cycles_into_hsync_ < 6);
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// Sync is taken to override pixels, and is combined as a simple OR.
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bool is_sync = state.hsync || state.vsync;
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bool is_sync = is_hsync || state.vsync;
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// If a transition between sync/border/pixels just occurred, flush whatever was
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// in progress to the CRT and reset counting.
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@ -238,7 +250,7 @@ class CRTCBusHandler {
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}
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}
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// check for a trailing hsync; if one occurred then that's the trigger potentially to change
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// check for a trailing CRTC hsync; if one occurred then that's the trigger potentially to change
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// modes, and should also be sent on to the interrupt timer
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if(was_hsync_ && !state.hsync) {
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if(mode_ != next_mode_) {
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@ -377,7 +389,10 @@ class CRTCBusHandler {
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}
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unsigned int cycles_;
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bool was_enabled_, was_sync_, was_hsync_, was_vsync_;
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int cycles_into_hsync_;
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std::shared_ptr<Outputs::CRT::CRT> crt_;
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uint8_t *pixel_data_, *pixel_pointer_;
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