HD66724 Datasheet, PDF (20/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
Address Counter (AC)
The address counter (AC) assigns addresses to DDRAM, CGRAM, or SEGRAM. When an address set
instruction is written into the IR, the address information is sent from the IR to the AC. Selection of
DDRAM, CGRAM, and SEGRAM is also determined concurrently by the RAM select bit (RM1/0).
After writing into (reading from) DDRAM, CGRAM, or SEGRAM, the AC is automatically incremented
by 1 (or decremented by 1). The cursor display position is determined by the address counter value.
Display Data RAM (DDRAM)
The display data RAM (DDRAM) stores display data represented in 8-bit character codes in the character
display mode. Its capacity is 80 × 8 bits, or 80 characters, which is equivalent to an area of 16 characters ×
5 lines. Any number of display lines (LCD drive duty ratio) from 1 to 3 can be selected by software. Here,
assignment of DDRAM addresses is the same for all display modes (table 5). The line to be displayed at the
top of the display (display-start line) can also be selected by register settings. The graphics display mode
does not use the data in the DDRAM.
Character Generator ROM (CGROM)
The character generator ROM (CGROM) generates 6 × 8-dot character patterns from 8-bit character codes.
It is equipped with a memory bank to generate 240 character patterns or 192 character patterns, which can
be switched according to applications. For details, see the CGROM Bank Switching Function section.
Table 6 illustrates the relation between character codes and character patterns for the Hitachi standard
CGROM. User-defined character patterns are also available using a mask-programmed ROM (see the
Modifying Character Patterns section).
Character Generator RAM (CGRAM)
The character generator RAM (CGRAM) allows the user to redefine the character patterns in the character
display mode. Up to 64 character patterns of 6 x 8-dot characters can be simultaneously displayed. The
DDRAM-specified character code can be selected to display one of these user font patterns.
The CGRAM serves as a RAM to store 72 x 24-dot (96 x 24-dot) bit pattern data in the graphics display
mode. Here, display patterns are directly written to the CGRAM. Character codes set in the DDRAM are
not used. For details, see the Graphics Display Function section.
Segment RAM (SEGRAM)
The segment RAM (SEGRAM) is used to enable control of segments such as icons and marks through the
user program. Segments and characters are driven by a multiplexing drive method.
The SEGRAM has a capacity of 96 × 2 bits, to control the display of a maximum of 144 (192) icons and
marks. While COMS1 and COMS2 outputs are being selected, the SEGRAM is read and segments (icons
and marks) are displayed by a multiplexing drive method (72 (96) segments each during COMS1 and
COMS2 selection).
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