Character Font Access Register

Register Name (address): CHARFONTACC (0x8402)

20023437

Bit 0

This is the Color Bit Plane Selector. This bit must be set to 0 to read or write a two-color attribute from the

range 0x0000 to 0x2FFF. When reading or writing four-color attributes from the range 0x3000 to 0x3FFF, this

bit is set to 0 for the least significant plane and to 1 for the most significant plane.

Bit 1

This is the Character/Attribute Selector. This applies to reads from the Display Page RAM (address range

0x8000–0x81FF). When a 0, the character code is returned and when a 1, the attribute code is returned.

Bits 7–2

Reserved. These should be set to zero.

Vertical Blank Duration Register

Register Name (address): VBLANKDUR (0x8403)

20023438

Bits 6–0

This register determines the duration of the vertical blanking signal in scan lines. When vertical blanking is

enabled, it is recommended that this register be set to a number greater than 0x0A.

Bit 7

Reserved. This bit should be set to zero.

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