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TM 11-5820-890-30-5
2-14. PRIMARY CONTROL SIGNALS. Continued
When the RT is transmitting, the T/R line is set to logic 1 by the control module. It checks the MED PWR, HI
PWR/M, and HI PWR/V lines from the RF switch. If none are at logic 1, the RT RF output is set for low power
operation. The SIG display circuit uses the RF DETECT, RF PWR A, RF PWR B, HI PWR XMT, PA PWR LVL, and T/R
lines during transmit to drive the display. The SIG STR RCV signal is used during receive.
During retransmit operation, all of the RXMT connector I/O is controlled by the switching module. See paragraph
2-17 for a description of retransmit operations.
The keyboard display is controlled by the control module. The SERIAL DATA, DISPLAY CLK, and DISP EN-N
provide the information needed by the display drivers. A DISPLAY INHIBIT line is used by the remote l/O to turn the
display off during remote operation.
The keyboard is made up of 16 switches (keys). They are arranged in a four-by-four switch matrix. The control
module checks the X and Y lines to see if a key has been pressed. The Y lines (rows) are normally at logic 1. The
X line (columns) are normally at logic 0. When a key is pressed, the Y line will be pulled to logic 0. The X line will
be pulled high (to about 6 V dc).
2-15. FREQUENCY HOPPING OPERATIONS.
The programming for FH operation is stored in the ECCM module ROM. The control module executes these
commands to control the RT while in FH.
Received FH signals are digital signals. The switching module digital processing produces bit synchronized data
(BS DATA). See figure 2-10. BS DATA is the RCV FH signal synchronized with the internal RT clocks and
converted to RT digital signal levels. BS DATA goes to the ECCM module interleave circuits. The interleaver
removes synchronization and frequency hopping information that is embedded in the signal. After
deinterleaving, the signal is reclocked at a 16 kb/s rate. It is now the FH DATA signal. In RCV DATA mode, FH
DATA is routed to the switching module. When receiving audio, FH DATA is converted back to an analog signal by
the continuously variable slope detector (CVSD) in the ECCM module. The RCV FH AUDIO output is also routed to
the switching module.
Two signals are required by the ECCM module during FH transmit. They are BS DATA and XMT PT AUDIO. BS
DATA goes directly to the interleave. It is interleaved with the synchronization and FH information needed by the
receiving RT to coordinate communications. The CVSD converts XMT PT AUDIO to a 16 kb/s digital signal output
as CVSD DATA to the interleave. It too is interleaved with data, reclocked to 20 kb/s, and output on the FH DATA
line to the switching module.
The interleave supplies the control and data signals needed by the time sync/correlator. The correlator’s
function is to synchronize the operation of the RT and the ECCM module. It manipulates control signal outputs
such as HOP TIME and SYNC. These and others control RT operations in FH mode. They shut down
reception/transmission during frequency shifts, provide the next frequency to the control module (via the data
and address buses), and supply clocking for the ECCM module.
The ECCM module is also responsible for: storage of the FH operation programming, generation of random
numbers for hopping frequency selection, and processing and storage of FILL data. The RT chooses the
frequencies in FH by pseudorandom number generation. The TRANSEC variable, FH sync time, and net ID
number are used to select the next frequency. The control module uses the hopset and lockout set to create a
look-up table in memory of frequencies for the net. The ECCM module picks one of these frequencies from the
table. The result is passed to the control module via the data bus. The control module informs the rest of the
modules of the frequency selected by the SERIAL DATA line.
2-18
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