■ 1.2 screen mode

● Screen mode and display range

• The screen mode and the coordinate values displayed at that time are as follows.

  Table 1.2 Screen mode and display range

  Screen mode	Range of X		Range of Y
  	standard	At high resolution
  Non-interlaced single-dense interlaced NTSC, PAL Width 320 x height 224 pixels Width 320 x height 240 pixels 352 horizontal x 224 vertical pixel 352 horizontal x 240 vertical pixels	0 ≤ X ≤ 319 0 ≤ X ≤ 319 0 ≤ X ≤ 351 0 ≤ X ≤ 351	0 ≤ X ≤ 639 0 ≤ X ≤ 639 0 ≤ X ≤ 703 0 ≤ X ≤ 703	0 ≤ Y ≤ 223 0 ≤ Y ≤ 239 0 ≤ Y ≤ 223 0 ≤ Y ≤ 239
  Dense interlace NTSC, PAL Width 320 x height 224 pixels Width 320 x height 240 pixels 352 horizontal x 224 vertical pixel 352 horizontal x 240 vertical pixels	0 ≤ X ≤ 319 0 ≤ X ≤ 319 0 ≤ X ≤ 351 0 ≤ X ≤ 351	0 ≤ X ≤ 639 0 ≤ X ≤ 639 0 ≤ X ≤ 703 0 ≤ X ≤ 703	0 ≤ Y ≤ 447 0 ≤ Y ≤ 479 0 ≤ Y ≤ 447 0 ≤ Y ≤ 479
  Non-interlaced 31kHz, HDTV Width 320 x height 240 pixels 352 horizontal x 240 vertical pixels	0 ≤ X ≤ 319 0 ≤ X ≤ 351		0 ≤ Y ≤ 239 0 ≤ Y ≤ 239

  However, this is a range of coordinates, not the size that occupies the framebuffer. For the size of the frame buffer, refer to "Frame Buffer ( 2.1 Address Map )".

• In the case of high resolution, it will be 8bit / pixel, which is half of the standard time. At this time, the rotation display of the frame buffer cannot be performed.

• The frame buffer cannot be rotated during double-dense interlacing.

• Interlace is one frame in both framebuffers when switching framebuffers for each field (double dense interlace).

• When switching the framebuffer every two fields (dense interlacing), the same picture is displayed in the even and odd fields. In either case, there will be no gap between the scan lines.

• At single-dense interlacing, the resolution is the same as at non-interlacing, and the method of writing to the frame buffer is the same.

• On 31kHz, HDTV, the same color is displayed in units of 4 pixels in total, 2 pixels vertically and 2 pixels horizontally. In other words, the resolution is the same as the standard 320 x 240 (31kHz) and 352 x 240 (HDTV), and the writing method to the frame buffer is also the same.

• Refer to the VDP2 User's Manual for how to set the interlace.

● Rotational read of frame buffer

• The entire frame buffer plane can be rotated and displayed by reading the frame buffer diagonally.
  

• The part where the display coordinates exceed the range of the frame buffer address is treated as transparent (XX00H at 8bit / pixel, 0000H at 16bit / pixel).

• Even if the frame buffer is rotated and read, the clipping area and erase light area are fixed with respect to the frame buffer plane. Therefore, the clipping area and erase light area will be tilted with respect to the display screen.

• In order to prevent the display screen from being chipped even if the frame buffer is rotated, the coordinate range of the frame buffer must be large. In this case, set the framebuffer to 8bit / pixel and the screen to 512x512 instead of 512x256. The number of simultaneous colors is 256 or less.

• Rotation is prohibited when setting normal, high resolution, HDTV, and double-dense interlace.

• The read start coordinates and read movement values for the rotary read of the frame buffer are received from VDP2.

• Rotational reading of the framebuffer is valid only for rotation 16 and rotation 8. Other than that, it is prohibited. Even if rotation data is sent from VDP2 during non-rotation, it is invalid and the parameter of VDP1 is valid.