HD64646FS datasheet(21/50 Pages) HITACHI

21 / 50 page

HD64645/64646

Character Mode and Graphic Mode

The LCTC supports two types of display modes; character mode and graphic mode. Graphic mode 2 is

provided to utilize software for a system using the CRTC (HD6845).

The display mode is controlled by an OR between the mode select pins (D/

S, G/C, LS, WIDE, AT) and

mode register (R22).

Character Mode: character mode displays characters by using CG-ROM. The display data supplied from

memory is accessed in 8-bit units. A variety of character attribute functions are provided, such as reverse

video, blinking, nondisplay (white or black), by storing the attribute data in attribute RAM (A-RAM).

Figure 10 illustrates the relation between character display screen and memory contents.

Graphic Mode 1: Graphic mode 1 directly displays data stored in a graphic memory buffer. The display

data supplied from memory is accessed in 16-bit units. Character attribute functions or wide mode are not

provided. Figure 11 illustrates the relation between graphic display screen and memory contents.

Graphic Mode 2: Graphic mode 2 utilizes software for a system using the CRTC (HD6845). The display

data supplied from memory is accessed in 16-bit units. Character attribute functions or wide mode are not

provided. The same memory addresses are output repeatedly the number of times specified by maximum

raster register (R9). The raster address is output in the same way as in character mode.

Reverse

video

Blinking

1st

row

2nd

row

VRAM

(char.

code)

ARAM

(Attr.

code)

8-bit

Reverse video

Blinking

Start

address

1st

row

2nd

row

Figure 10 Relation between Character Screen and Memory Contents

HD64646FS Datasheet(PDF) 21 Page - Hitachi Semiconductor