Fluke 93 - Lcd

3-12
CIRCUIT DESCRIPTIONS
this way capacitor C1312 is charged
Just
enough to keep the output voltage -fVRAM at a stable value
{
3V DC).
sie*u
Figure 3. 6 Pulse trein signal on input A of Schmitt input HAND (Test Point 223)
3.3.5 LCD circuitry
•
Introduction
The LCD used in the ScopeMeter is controlled by six LCD driver integrated circuits. These drivers get
their information (data- and control signals) directly from the D-ASIC. The microprocessor enables
the display when valid data is present.
ScopeMeter
models 93 and 95 use a reflexive LCD.
Model 97
Is
provided
with
atransflexive
LCD
with
a backlight, which can be switched on or off by the user.
•
Detailed circuit description
See figure circuit diagram A1 (figure 10.2),
LCD
The ScopeMeter uses a Super Twisted Nematic Liquid Crystal Display (LCD HI 401. see circuit
diagram
A1,
figure
10.2),
with
a
resolution of 240
*
240
pixels.
The picture on the LCD screen is written column (vertical line) after column, rather hian row
(horizontal line) after row. The LCD screen is divided horizontally In 3 row-sections, each
60
pixels
wide and vertically into 3 column-secUons, each
60
pixels
wide.
LCD drivers
The LCD display is controlled by the D-ASIC, via six LCD drivers:
-
three LCD row drivers: D1404, D1406, D1407
>
three LCD column drivers: D1401, D1402, D1403
Description of the LCD drivers lnput-/output signals:
LCD outputs Yt... YSO and X1...XS0
These outputs are connected to the LCD
matrix. Every
column
driver
serves
80
pixel columns of the
LCD. Every row driver serves
80
pixel rows. The output signals are staircase
signals,
with
levels
equal to the VI ...V6 voltages.
NOTE: On the ouput of every LCD driver, a Test Point is provided (TP207...TP212). When the driver
is working property, a staircase voltage can be measured on these test points.
•
Data inputs D0...D3 (row drivers only!)
The actual display data coming from the D-ASIC
is
sent via
the DRIVERBUS
to
the
LCD
drivers
D0...D3 inputs.
•
Terminai input voitagee V1...V6
Out of these DC signals, with
^
-20
V,
the
LCD
drivers generate the staircase signals. The input
voltages
Vi...ve
are
generated
by
die
LCD
supply section.