Theory of Operation
2 - 28
68P02963C70-O
Display and Keypad Description
Display
The LCD (Liquid Crystal Display) Module is a Graphic Display based upon the
KS0741TB-01 display driver.
It consist of LCD Holographic Glass, LED backlight and a 22 pin flex cable con-
nected to the Keypad board.
The Communication to the RedCap2 IC is performed using a SPI protocol (Serial
Peripheral Interface). The Operation of the LCD is determined upon the RS line
configuration (Data/Command).
The Display is 128X100 (Columns X Rows respectively).
Keypad
The RCE is responsible for decoding key presses and displaying them properly on
the LCD. The keys are arranged into a matrix of five rows and five columns, which
includes the Volume and PTT keys.
The PWR key is not decoded by the RCE; it directly drives the GCAP III, which
sends a signal to RCE through INT1. The five row lines are pulled high via five
internal 22 Kohm resistors. The five row lines and five column lines are fed to
REDCAP2 I/O pins. Pressing any key also generates the keypad internal interrupt.
The REDCAP2 debounces the keys by reading them 25 milliseconds later.
The keypad-decoding scheme works as follows:
1.
REDCAP2 sets rows to inputs; all columns are set as outputs and driven
logic low.
2.
Rows are pulled logic high. When a key is pressed, one row goes low,
which indicates a key press and sends an internal interrupt.
3.
REDCAP2 reads rows. A low on that row indicates a key press. All others
are high.
4.
REDCAP2 sets all columns to output logic high.
5.
One column at a time is set to output logic low. REDCAP2 reads the rows
to see which one is now at a logic low level. (A low seen on a row indicates
the correct column and row.)
All keypad circuitry is located on the keypad board. Refer to the keypad board
schematics.
Содержание MTH500
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Страница 76: ...Troubleshooting 3 26 68P02963C70 O Offset VCO Test ...
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Страница 100: ...Maintenance 5 18 68P02963C70 O Figure 23 Exploded View 1 2 3 4 5 7 6 X6 8 ...
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Страница 103: ...MTH500 Detailed Service Manual COMPONENT BOARD LAYOUTS 68P02963C70 O 6 1 Component Board Layouts ...
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Страница 109: ...MTH500 Detailed Service Manual Schematic Diagrams and Parts Lists 68P02963C70 O 6 7 Schematic Diagrams and Parts Lists ...
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