HD66710 Datasheet, PDF (21/73 Pages) Hitachi Semiconductor – (Dot Matrix Liquid Crystal Display Controller/Driver)

HD66710
 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. (EPROM addresses 00H to FFH.)
3. Treatment of unused user patterns in the HD66710 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 5
Example of Correspondence between Character Code and Character Pattern (5 × 8
Dots) in CGRAM
a) When Character Pattern in 5 × 8 Dots
Character code (DDRAM data)
CGRAM address
MSB CGRAM data
LSB
D7 D6 D5 D4 D3 D2 D1 D0 A5 A4 A3 A2 A1 A0 O7 O6 O5 O4 O3 O2 O1 O0
0000*000
000
000
001
010
011
100
101
110
111
***
10001
10001
10001
01010
00100
00100
00100
00000
0000*111
111
000
001
010
011
100
101
110
111
***
10001
10001
10001
01010
00100
00100
00100
00000
Character
pattern
(1)
Character
pattern
(8)
311