On CRTC 2, if a VSYNC is triggered during an HSYNC, the CRTC produces a ghost VSYNC. The CRTC then counts the lines as if a VSYNC were taking place by preventing a new VSYNC from occurring, but without the VSYNC pin being enabled.
==== Mid-VSYNC ====
On all CRTCs, in both interlace modes, a Mid-VSYNC is generated when VCC=R7 on the even frame. The VSYNC pulse starts in the middle of the rasterline, at HCC=R0/2.
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