mirror of https://github.com/bsnes-emu/bsnes.git
50 lines
1.5 KiB
C++
50 lines
1.5 KiB
C++
//PPUcounter emulates the H/V latch counters of the S-PPU2.
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//
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//real hardware has the S-CPU maintain its own copy of these counters that are
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//updated based on the state of the S-PPU Vblank and Hblank pins. emulating this
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//would require full lock-step synchronization for every clock tick.
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//to bypass this and allow the two to run out-of-order, both the CPU and PPU
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//classes inherit PPUcounter and keep their own counters.
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//the timers are kept in sync, as the only differences occur on V=240 and V=261,
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//based on interlace. thus, we need only synchronize and fetch interlace at any
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//point before this in the frame, which is handled internally by this class at
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//V=128.
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struct PPUcounter {
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alwaysinline auto tick() -> void;
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alwaysinline auto tick(uint clocks) -> void;
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alwaysinline auto field() const -> bool;
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alwaysinline auto vcounter() const -> uint16;
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alwaysinline auto hcounter() const -> uint16;
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inline auto hdot() const -> uint16;
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inline auto lineclocks() const -> uint16;
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alwaysinline auto field(uint offset) const -> bool;
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alwaysinline auto vcounter(uint offset) const -> uint16;
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alwaysinline auto hcounter(uint offset) const -> uint16;
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inline auto reset() -> void;
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auto serialize(serializer&) -> void;
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function<auto () -> void> scanline;
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private:
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inline auto vcounterTick() -> void;
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struct {
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bool interlace;
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bool field;
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uint16 vcounter;
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uint16 hcounter;
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} status;
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struct {
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bool field[2048];
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uint16 vcounter[2048];
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uint16 hcounter[2048];
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int32 index;
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} history;
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};
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