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49 lines
1.6 KiB
C++
49 lines
1.6 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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class PPUcounter {
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public:
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alwaysinline void tick();
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alwaysinline void tick(unsigned clocks);
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alwaysinline bool field () const;
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alwaysinline uint16 vcounter() const;
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alwaysinline uint16 hcounter() const;
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alwaysinline uint8 framecounter() const;
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alwaysinline uint16 lineclocks() const;
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alwaysinline uint16 prev_lineclocks() const;
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alwaysinline uint16 fieldlines() const;
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inline uint16 hdot() const;
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alwaysinline uint16 vcounter_future(unsigned offset) const;
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alwaysinline uint16 vcounter_past(unsigned offset) const;
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alwaysinline uint16 hcounter_past(unsigned offset) const;
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inline void reset();
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function<void ()> scanline;
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void serialize(serializer&);
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private:
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inline void vcounter_tick();
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inline void frame_tick();
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struct {
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uint16 hcounter;
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uint16 vcounter;
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uint8 frame;
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uint16 lineclocks;
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uint16 prev_lineclocks;
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uint16 fieldlines[2];
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bool field;
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} status;
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};
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