4: Theory of Operation
4-4
TW7201I-MS
Front Panel
Keypad
Pressing a key on the front panel Keypad asserts a row line that connects to
multiplexer U11 and a column line connected to muliplexer U12. These
muliplexers send a pulse to U12 pin 3 that stops the keypad oscillator U19C.
The oscillator drives counter U9 which scans the row and column lines. When
the keypad scanning stops, shift register U10 records the count at the point it
stops; this corresponds to a unique key. After reading the key, the processor
restarts the scanning loop by toggling U3 pin 7.
Configuration
Jumper Block
Jumper block J11 provides configuration settings for front panel functions.
Multiplexer U2 converts the parallel settings to serial data that the processor
reads at power up. Table 4-1 below lists the functions controlled by the J11
jumper block.
4.2.2
Switch Board
The Switch Matrix board attaches to the front panel and provides an interface
for the keypad alphanumeric keys.
4.2.3
Keypad
The Keypad attaches to the front panel and provides a way for the operator to
interface with the TW7000 transceiver through the TW7201I using
alphanumeric keys.
4.2.4
Display Board
The Display board attaches to the front panel and includes the LCD and
display drivers for the LCD. It also includes a serial to parallel driver that
takes serial transmit data in U3 and provides parallel data for the display bar
graph and other indicators.
The LCD is a high resolution back-lit alphanumeric display that provides
channel number, channel frequency, time, clarifier offset, mode and relative
signal strength/output power, as well as the status of available options. Two
Table 4-1 Jumper Block J11 Default Settings
Jumper
Function
Default
1
All function lockout
Off
2
Frequency change lockout
Off
3
Frequency display lockout
Off
4
Mode change lockout
Off
5
Power change lockout
Off
6
PTT lockout
Off
7
CW lockout
Off
8
TW7000 lockout
Off
9
Not assigned
Off
10
Not assigned
Off
Summary of Contents for TW7201I
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Page 99: ...TW7201I MS Figure 5 6 Power Supply Interface Schematic Diagram 994222 Rev D 5 39 ...
Page 104: ...TW7201I MS TW7201I MS Figure 5 8 Switching Board Schematic Diagram 994149 Rev A 5 45 ...
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