hd66712u Renesas Electronics Corporation., hd66712u Datasheet - Page 22

• Manufacturer Part Number: hd66712u
• Description: Dot-matrix Liquid Crystal Display Controller/driver - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

HD66712U
Character Generator ROM (CGROM)
The character generator ROM generates 5
8 dot character patterns from 8-bit character codes (Table 3
to 6). It can generate 240 5
8 dot character patterns. User-defined character patterns are also available
using a mask-programmed ROM (see “Modifying Character Patterns.”)
Character Generator RAM (CGRAM)
The character generator RAM allows the user to redefine the character patterns. In the case of 5
8
characters, up to eight may be redefined.
Write the character codes at the addresses shown as the left column of Table 3 to 6 to show the character
patterns stored in CGRAM.
See Table 7 for the relationship between CGRAM addresses and data and display patterns.
Segment RAM (SEGRAM)
The segment RAM (SEGRAM) is used to enable control of segments such as an icon and a mark by the
user program.
For a 1-line display, SEGRAM is read from the COM0 and the COM17 output, and for 2- or 4-line
displays, it is read from the COM0 and the COM33 output, to perform 60-segment display (80-segment
display when using the extension driver).
As shown in Table 8, bits in SEGRAM corresponding to segments to be displayed are directly set by the
MPU, regardless of the contents of DDRAM and CGRAM.
SEGRAM data is stored in eight bits. The lower six bits control the display of each segment, and the
upper two bits control segment blinking.
Timing Generation Circuit
The timing generation circuit generates timing signals for the operation of internal circuits such as
DDRAM, CGROM, CGRAM, and SEGRAM. RAM read timing for display and internal operation timing
by MPU access are generated separately to avoid interfering with each other. Therefore, when writing
data to DDRAM, for example, there will be no undesirable interferences, such as flickering, in areas
other than the display area.
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