End bit fetch status in the previous frame: before end-bit fetch status (BEF), bit 0
Indicates whether the end bit (drawing end command) was fetched from the command table in the previous frame. When it is 0, the end bit indicates an unfetched state, and when it is 1, it indicates that the end bit has been fetched and drawing has ended.
BEF
End bit fetch status
0
End bit unfetched in previous frame
1
End bit fetch and rendering in previous frame
VDP1 fetches the command table in VRAM one after another and draws it in the frame buffer. When the drawing end command (end bit is 1) is fetched, drawing processing for one frame is completed. If there are many commands or there are many pixels to be drawn for enlargement, drawing may not be completed within one frame. This is called “transfer over”. This bit indicates a transfer over condition.
When transfer is over, measures such as reducing drawing commands or drawing pixels are required.
If there is no drawing end command in VRAM, this bit will remain 0 if it is defined so that it cannot be fetched in jump format.
The CEF value is written to this bit when the frame buffer is switched or when drawing starts, and is retained until the next frame buffer switch.