Circuit Descriptions
1502C MTDR Service Manual
5–29
The display module function is to take bit pattern data generated by the instrument
internal electronics and display it on the LCD. A block diagram of the display
module is shown in Figure 5–14.
DATA/CONTROL
DISPLAY
MEMORY
4K X 8
ADDR
ADDR
DATA
CONTROLLER
40-PIN CONNECTOR
ROW
DRIVER
column driver [4]
column driver [4]
upper
lower
SBE CELL
128 X 256
board-to-board
elastomer
flex cable
column
elastomer
column
elastomer
64 64 64 64
64 64 64 64
64
64
ROW DRIVER/CONTROLLER BOARD COLUMN DRIVER BOARD
DATA/CONTROL
Figure 5–14: Display Module Block Diagram
The LCD cell is the “video screen” that displays information generated by the
processor. The processor updates the display memory periodically with a new
picture and the display memory holds this bit pattern data. This data is received by
the display controller and sent to the drivers along with some control and timing
signals that provide operating information to the drivers. The row and column
drivers are attached electrically to the LCD cell through elastomeric connectors and
a flex cable. These drivers place signal voltages on the electrode matrix in the LCD
cell and thus generate the video display.
There are other circuits contained in the display module. An indium tin oxide (ITO)
heater warms the display during cold temperatures. A temperature sensor attached
to the display provides display temperature data to the heater and drive voltage
circuitry (see Front Panel text in this chapter). An electroluminescent backlight
provides illumination in low light conditions.
The LCD cell provided in the 1502C uses an advanced technology known as
Superbirefringent Effect (SBE) to obtain greatly improved contrast and viewing
LCD Cell
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