HD66712 Datasheet, PDF (34/88 Pages) Hitachi Semiconductor – Dot-Matrix Liquid Crystal Display Controller/Driver

HD66712U
Programming Character Patterns
This section explains the correspondence between addresses and data used to program character patterns
in EPROM.
• Programming to EPROM
The HD66712 character generator ROM can generate 240 5 × 8 dot character patterns. Table 9 shows
correspondence between the EPROM address data and the character pattern.
Handling Unused Character Patterns
1. EPROM data outside the character pattern area: This is ignored by the character generator ROM for
display operation so any data is acceptable.
2. EPROM data in CGRAM area: Always fill with zeros.
3. Treatment of unused user patterns in the HD66712 EPROM: According to the user application, these
are handled in either of two ways:
a When unused character patterns are not programmed: If an unused character code is written into
DDRAM, all its dots are lit, because the EPROM is filled with 1s after it is erased.
b When unused character patterns are programmed as 0s: Nothing is displayed even if unused
character codes are written into DDRAM. (This is equivalent to a space.)
Table 9
Example of Correspondence between EPROM Address Data and Character Pattern
(5 × 8 Dots)
EPROM Address
A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
0 1 0 1 10 0 1 0 0 0 0
0 001
0 010
0 011
0 100
0 101
0 110
0 111
MSB
Data
LSB
O4 O3 O2 O1 O0
1 0001
1 0001
1 0001
01 010
0 0100
0 0100
0 0100
0 0000
Character code
“0” Line position
Notes: 1. EPROM addresses A11 to A4 correspond to a character code.
2. EPROM addresses A2 to A0 specify the line position of the character pattern. EPROM address
A3 should be set to “0.”
3. EPROM data O4 to O0 correspond to character pattern data.
4. Areas which are lit (indicated by shading) are stored as “1,” and unlit areas as “0.”
5. The eighth line is also stored in the CGROM, and should also be programmed. If the eighth line
is used for a cursor, this data should all be set to zero.
6. EPROM data bits 07 to 05 are invalid. 0 should be written in all bits.
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