★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 4 Scroll screen
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VDP2 User's Manual / Chapter 4 Scroll Screen

■ 4.10 Display area

The display area of the scroll screen changes depending on the register settings. If the display coordinate value exceeds the display area on the normal scroll screen, the image in the display area is displayed repeatedly. If the display coordinate value exceeds the display area on the rotation scroll screen, it is processed according to the register settings.

● Display area

The display area changes depending on the plane size when the scroll screen display format is cell format, and changes depending on the bitmap size when the bitmap format is used. For NBG0 and NBG1, it also changes depending on the setting of reduced display up to 1/4. The display areas are shown in Tables 4.12 and 4.13.

Table 4.12 Normal scroll screen display area
Display format Reduction setting Plain size Bitmap size Display area
Cell format No reduction or
Up to 1/2 possible		 Horizontal 1 page ×
1 vertical page		 − 0 ≤ X <1024, 0 ≤ Y <1024
Horizontal 2 pages ×
1 vertical page		 − 0 ≤ X <2048, 0 ≤ Y <1024
Horizontal 2 pages ×
2 vertical pages		 − 0 ≤ X <2048, 0 ≤ Y <2048
Up to 1/4 possible Horizontal 1 page ×
1 vertical page		 − 0 ≤ X <1024, 0 ≤ Y <2048
Horizontal 2 pages ×
1 vertical page		 − 0 ≤ X <2048, 0 ≤ Y <2048
Bitmap format − − Horizontal 512 dots x
Vertical 256 dots		 0 ≤ X <512, 0 ≤ Y <256
− Horizontal 512 dots x
512 dots vertically		 0 ≤ X <512, 0 ≤ Y <512
− 1024 dots wide x
Vertical 256 dots		 0 ≤ X <1024, 0 ≤ Y <256
− 1024 dots wide x
512 dots vertically		 0 ≤ X <1024, 0 ≤ Y <512

Table 4.13 Display area of rotary scroll screen
Display format Plain size Bitmap size Display area
Cell format Horizontal 1 page ×
1 vertical page		 − 0 ≤ X <2048, 0 ≤ Y <2048
Horizontal 2 pages ×
1 vertical page		 − 0 ≤ X <4096, 0 ≤ Y <2048
Horizontal 2 pages ×
2 vertical pages		 − 0 ≤ X <4096, 0 ≤ Y <4096
Bitmap format − Horizontal 512 dots x
Vertical 256 dots		 0 ≤ X <512, 0 ≤ Y <256
− Horizontal 512 dots x
512 dots vertically		 0 ≤ X <512, 0 ≤ Y <512

● Screen over processing

When displaying the rotation scroll screen, if the display coordinate value of the calculation result exceeds the specified display area, select one of the following four and set it in the register. The screen over processing is set not for RBG0 and RBG1 but for the scroll screen with rotation parameter A and the scroll screen with rotation parameter B.

  1. Outside the display area, the image set in the display area is repeated.

  2. Outside the display area, the character pattern specified in the screen over pattern name register is repeated (only when the rotating scroll screen is in cell format).

  3. Make everything outside the display area transparent.

  4. Forcibly set the display area to 0 ≤ X <512, 0 ≤ Y <512 regardless of the plane size or bitmap size, and make everything outside the area transparent.

● Screen over pattern name

The pattern name data when the screen over processing setting is set to repeat the specified character pattern is specified in the 16-bit screen over pattern name register. The screen over pattern name data specified in the register is treated in the same way as when the data size of the pattern name table on the scroll surface is 1 word, and the bits that are insufficient using the auxiliary data of the lower 10 bits of the pattern name control register. To make a total of 26-bit screen over pattern name data. The bit configuration of the screen over pattern name register is the same as when the pattern name data size is 1 word, as shown in " Pattern name data " in "4.6 Pattern name table", and the character size, number of character colors, and characters It depends on the number auxiliary mode. Also, the size of the repeated character pattern depends on the character size setting.
16-bit screen over pattern name data is specified for the scroll screen by rotation parameter A and scroll screen by rotation parameter B, but the 10-bit auxiliary data specified by the pattern name control register is for RBG0 and RBG1. Please note that you specify. In addition, the screen over pattern name data cannot be used when displaying the rotating scroll screen in bitmap format.

● Screen over pattern name register

The screen over pattern name register specifies the pattern name data when the rotation scroll screen is set to repeat the character pattern in the screen over processing. This is a write-only 16-bit register located at addresses 1800B8H to 1800BAH. After turning on the power or resetting, the value will be cleared to 0, so be sure to set it.

OVPNRA 1800B8H
 15
 14
 13
 12
 11
 Ten
 09 09
 08 08
 RAOPN15
 RAOPN14
 RAOPN13
 RAOPN12
 RAOPN11
 RAOPN10
 RAOPN9
 RAOPN8

 07 07
 06 06
 05 05
 04
 03 03
 02 02
 01 01
 00
 RAOPN7
 RAOPN6
 RAOPN5
 RAOPN4
 RAOPN3
 RAOPN2
 RAOPN1
 RAOPN0

OVPNRB 1800BAH
 15
 14
 13
 12
 11
 Ten
 09 09
 08 08
 RBOPN15
 RBOPN14
 RBOPN13
 RBOPN12
 RBOPN11
 RBOPN10
 RBOPN9
 RBOPN8

 07 07
 06 06
 05 05
 04
 03 03
 02 02
 01 01
 00
 RBOPN7
 RBOPN6
 RBOPN5
 RBOPN4
 RBOPN3
 RBOPN2
 RBOPN1
 RBOPN0

　　

Over pattern name bit : Over pattern name bit (RAOPN15 to RAOPN0, RBOPN15 to RBOPN0)
Specify the pattern name data when screen over processing that repeats the character pattern is set.

RAOPN15 ~ RAOPN0 1800B8H Bits 15-0 For rotation parameter A
RBOPN15 ~ RBOPN0 1800BAH Bits 15-0 For rotation parameter B

The bit configuration is the same as when the data size of the pattern name table is 1 word, and it depends on the character size, the number of character colors, and the character number auxiliary mode setting.
This register is performed for the scroll screen with rotation parameter A and the scroll screen with rotation parameter B, but the character size and character number auxiliary modes that determine the bit configuration are performed for RBG0 and RBG1. Therefore, be careful when displaying the screen with rotation parameter A and rotation parameter B on RBG0 at the same time.

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★ HARDWARE Manual VDP2 User's Manual ★ Chapter 4 Scroll screen
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