ST7920
Display Data RAM (DDRAM)
There are 64x2 bytes RAM spaces for the Display Data RAM. It can store display data such as 16 characters (16x16)
by 4 lines or 32 characters (8x16) by 4 lines. However, only 2 character-lines (maximum 32 common outputs) can be
displayed at one time. Character codes stored in DDRAM will refer to the fonts specified by CGROM, HCGROM and
CGRAM.
ST7920 can display half-width HCGROM fonts, user-defined CGRAM fonts and full 16x16 CGROM fonts. The
character codes in 0000H~0006H will use user-defined fonts in CGRAM. The character codes in 02H~7FH will use
half-width alpha numeric fonts. The character code larger than A1H will be treated as 16x16 fonts and will be
combined with the next byte automatically. The 16x16 BIG5 fonts are stored in A140H~D75FH while the 16x16 GB
fonts are stored in A1A0H~F7FFH. In short:
1. To display HCGROM fonts:
Write 2 bytes of data into DDRAM to display two 8x16 fonts. Each byte represents 1 character.
The data is among 02H~7FH.
2. To display CGRAM fonts:
Write 2 bytes of data into DDRAM to display one 16x16 font.
Only 0000H, 0002H, 0004H and 0006H are acceptable.
3. To display CGROM fonts:
Write 2 bytes of data into DDRAM to display one 16x16 font.
A140H~D75FH are BIG5 code, A1A0H~F7FFH are GB code.
The higher byte (D15~D8) is written first and the lower byte (D7~D0) is the next.
Please refer to Table 5 for the relationship between DDRAM and the address/data of CGRAM.
CGRAM fonts and CGROM fonts can only be displayed in the start position of each address. (Refer toTable 4)
80
81
82
83
84
85
86
87
88
89
8A
8B
8C
8D
8E
8F
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H
L
H L H L H L H L H L H L
S
矽
i
t
r
o
n
i
x
S
.
.
T
.
7
9
2
0
創
創
電
電
子
子
中
文
編
碼
正
確
.
.
(
)
矽
中
文
編
碼
Table 4
Incorrect start position
V4.0
11/49
2008/08/18
SITRONIX [ SITRONIX TECHNOLOGY CO., LTD. ]
