LCD-IV----------------------------------------------------~--------------
•
LIQUID
CRYSTAL
DISPLAY
• Liquid Crystal Display Circuit
The LCD-IV can directly drive the liquid crystal display
panel of static, 1/2 duty factor, 1/3 duty factor and 1/4 duty
factor.
R
so
,
Rn
t;
W
-J
W
CI)
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~
a::
>
~
-J
CL
CI)
o
DISPLAY
COUNTER &
CONTROL
CIRCUIT
RIIO
X,Y
C)
z
~
1--'---.l\.lw
I---r----./I
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o
~
The LCD-IV has 4 common signal terminals and 32 seg·
ment signal terminals. Further,
if
liquid crystal driver LSI
(H044100H) is connected to the LCD-IV, up
to
96 segment
signal terminals can be extended externally. Thus, in addition
to the internal 32 terminals, total 128 segment signal terminals
can be driven.
51
BUS
52
BUS
RAM
SERIAL
DATA
ALTERNATING
SIGNAL
(M)
SERIAL
SEGMENT
DATA
(D)
Figure 25 Liquid Crystal Display Circuit Block Diagram
Display
is
automatically executed by writing segment data
into
RAM
for
LCD.
The
RAM
reads segment data bit by bit
sequentially every one instruction cycle upon receiving address
signal from the display counter and the control circuit. Every
time common signal
is
scanned, the
RAM
reads 128-segment
data
(SEG
t
to
SEG
t
28),
which
is
correspond
to
common signal
selected at the next time.
Scan
of
common
signal
is
executed
every 256-instruction cycle. Therefore, the data which
is
cor·
respond to 128-segment
is
read twice at the
same
time. The
serial data read
is
converted to parallel data by the shift register
and latch, converted to
LCD
drive
signal
by the
liqUid
crystal
driver and the outputted from a segment terminal. 32-segment
(SEGI to SEG32) out
of
128.segment serial data
is
used within
the
LCD·IV, and the rest (96-segment)
is
outputted
to
liquid
crystal driver LSI
HD44100H which is connected
to
the LCD·
IV and is converted
to
LCD
drive signal in the HD44100H at
the time
of
designation
of
with liquid crystal segment output
extension.
Cycle
of
the latch clock
is
256-instruction cycle in
the
LCD-IV. In the case
of
dynamic drive, data at the common
side changes synchronously with the latch clock. These display
operations are all executed regardless
of
program.
202
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