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Chapter 8 Window

8.1 Window area

There are two normal windows (W0, W1) and one sprite window (SW) in the scroll IC window. The normal window is specified by the start point and end point coordinates on the TV screen, and the sprite window is specified by the value of the most significant bit of the sprite data written to the frame buffer. Each window can specify for which scrolling screen it will be active and whether the inner or outer area will be active. When multiple windows are enabled, they can be overlapped with AND or OR logic.
∙ For the normal window, you can select either the normal rectangular window specified by the horizontal and vertical start and end coordinates, or the normal line window that specifies the horizontal start and end coordinates for each line. The start point and end point coordinates are not coordinate values ​​on the scroll screen, but coordinate values ​​on the TV screen are set in each register.

■ Normal rectangular window

A normal rectangular window can be obtained by specifying the start point coordinates of the upper left corner and the end point coordinates of the lower right corner of the window in the window position register. The area enclosed by the specified coordinates is inside, and the other area is outside. The window border is considered inside.
∙ If the start point coordinate is larger than the end point coordinate in either the horizontal direction or the vertical direction, the entire screen will be judged as the area outside the window.
The normal rectangular window is shown in Figure 8.1.

Figure 8.1 Normal rectangular window

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