Data Sheet

Broadcom AV02-0629EN
11
HDSP-210x/-211x/-250x Series Data Sheet Eight-Character 5 mm and 7 mm Smart Alphanumeric Displays
Character RAM
Figure 7 shows the logic levels needed to access the HDSP-210X/-211X/-250X Character RAM. During a normal access,
the CE
= 0 and either RD = 0 or WR = 0. However, erroneous data may be written into the Character RAM if the address
lines are unstable when CE
= 0 regardless of the logic levels of the RD or WR lines. Address lines A
0
–A
2
are used to select
the location in the Character RAM. Two types of data can be stored in each Character RAM location: an ASCII code or a
UDC RAM address. Data bit D
7
is used to differentiate between the ASCII character and a UDC RAM address. D
7
= 0
enables the ASCII decoder and D
7
= 1 enables the UDC RAM. D
0
–D
6
are used to input ASCII data and D
0
–D
3
are used to
input a UDC address.
Figure 7: Logic Levels to Access the Character RAM
CE
FL A
4
A
3
A
2
A
1
A
0
RST WR RD
Character
Address
Symbol is accessed in location
spcified by the character address above
01
00
01
1
111
0
11
Undefined
Control Signals
Character RAM Address
Character RAM Data Format
Write to Display
Read from Display
Undefined
000 = Left most
111 = Right most
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
0 128 ASCII Code
X XX UDC Code1
Display
0 = Logic 0; 1 = Logic 1; X = Do Not Care
DIG
0
DIG
1
DIG
2
DIG
3
DIG
4
DIG
5
DIG
6
DIG
7
001 010 011 100 101 110 111000