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SC204A
VER2.1
5. Operating Principles
a) Pin description
Pin NO.
Symbol
Level
Function
1
VSS
0V
Ground
2
VDD
4.5V~5.5V
Supply voltage for logic
3
V0
Variable voltage for LCD
4
RS
H/L
H: Instruction code
L: Data
5
R/W
H/L
H: Read signal L: Write signal
6
E
H→L
enable signal
7
DB0
H/L
8
DB1
H/L
9
DB2
H/L
10
DB3
H/L
11
DB4
H/L
12
DB5
H/L
13
DB6
H/L
14
DB7
H/L
Data bits
In case of
4 bits instruction, data is
transferred by twice using only 4 buses of D4
– D7 ,and D0 – D3 are not used
,
first
operation is higher order
4 bits and
second
is
lower
4
bits of
8 bits ,
but in case
of
8
bits
instruction
, data
is
transferred by
data by
data bus
of
D0 –
D7
15
BLA(+)
4.2V
Supply voltage for LED-Backlight
16
BLK(-)
0V
Supply voltage for LED-Backlight
b) Block Diagram
IR
I/O
B
U
F
F
E
R
LCD
Driving Circuit
P TO S registor
BUSY
FLAG
DR
CG RAM
CG
RAM
Cursor
and
blink
CKT.
COM
Driving
Circuit
DD RAM
AC
Timing Control Circuit
D
E
C
O
D
E
R
RS
R/W
E
D0-D3
D4-D7
VDD
VO
VSS
a. Data Register (DR): Dris a register used for temporary Storage of the data read/write form/into DD
RAM and CG RAM.
b. Instruction Register (IR): is a register available for storing the instruction codes and address
information of display data (DD) RAM and character generator (CG) RAM.
c. BUSY FLAG (BF): When the Busy Flag is “1”,it shows that LCM is in internal operation and it can
not accept the next instruction.
d. Character Generator (CG) ROM: This ROM Generates character pattern from 8-bit character code
and provides 192 character patterns.
e. Character Generator (CG)RAM: This RAM allows the user to rewrite the character patterns freely
according to the program.
f.
Address Counter (AC): This address counter is used to give the address information of DD RAM
and CG RAM.
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