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Block Diagram Descriptions
CSA 803C Service Manual
3Ć15
A9 Touch Panel Assembly
This circuit Is comprised of infrared LEDs that produce a matrix of light
beams that are interrupted when the user touches a particular touch zone.
The touch panel and hard key matrix are scanned continuously until a
shadow or keypress is detected. When a hit is detected, that scan is comĆ
pleted and the interrupt line is asserted by the display controller. During this
time, the interrupt is active and no new data is written into the sensor RAM
from the touch panel or hard keys, even though the hardware continues to
scan; therefore, the data will not change in the sensor RAM while the microĆ
processor is reading it.
Only one infrared LED is turned on at a time and only the phototransistor
directly opposite is selected to receive light. This prevents any crosstalk
between emitter/detector pairs.
A10 Front Panel Control Board
This circuitry generates the 6Ćbit address bus that is used to select an inĆ
frared LED and its compliment phototransistor on the A9 Touch Panel board.
A11 Front Panel Button Board
This circuitry Is comprised of the major menu LED light bars that are driven
by the display refresh register output of the A7 Display Controller board.
Internally, there is a matrix of display RAM organized in an 8Ćbit by 8Ćbit
matrix. This display RAM is scanned column by column (automatically),
lighting the appropriate LED bar(s) when a high bit is encountered. The
coarse/fine LEDs are driven by a latch that is controlled by the EXP. The
coarse/fine selections are sensed on the A9 Touch Panel board.