Satellite Tc Request - Safran CORTEX CRT Quantum User Manual

3.5.1.1. Satellite TC Request

Used for sending any number of bits, according to the user-defined modulation characteristics: FSK or PSK
modulation, PCM code, bit rate, sub-carrier frequency. The TC message is stored in the TC encoder on the TCU
for potential repetition.
The TC message to send is split into 32-bit words, but the exact number of bits to send may be any number. The
MSB of each word is modulated first. The TC message to transmit is supposed to include all necessary
synchronisation word, on-board decoder address, spare bit, data word, command CRC, but does not include any
preamble or idle pattern.
At the time the satellite TC request is received, the command encoder may be:
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If the command encoder is stopped: it first rises the carrier for the duration specified in parameter RF set time
(this time may be shortened in the case where parameter CMM1 CLCW is on and when CMM1 flag in the
telemetry matches the expected value).
Then, the command encoder modulates the preamble (the preamble structure is fixed: 1010101010... and the
preamble length is programmable via the Control port), and if parameter CMM2 CLCW is on, it checks the
corresponding bit(s) in the telemetry and then modulates the TC message. Should any check fail, the sequence
is aborted Refer to Figure 69 for more detail.
Note: in BPSK mode, it is possible to pre-transmit the unmodulated BPSK sub-carrier for a programmable
number of bits (see Section 4.2.8.5.1), before transmitting the data (Sub-carrier modulation).
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Should idling be inserted between two consecutive TC messages, the idle pattern may be explicitly inserted at
the end of the first one, or at the beginning of the last one, or a « Pause » instruction may be inserted between
the two satellite TC requests.
Each operation is executed once the previous is finished.
If no more satellite TC request is awaiting or if a « Wait & Verify » or « Pause » or « Wait for Absolute Time »
instruction is received, the command encoder turns to idling, except if it received a « Stop Idling » instruction.
When idling, the command encoder always modulates an integer number of idle patterns as defined by the
control parameters.
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stopped,
or idling,
or modulating a TC message.
If the command encoder is idling: it waits for the current idle pattern to be fully
transmitted (idle pattern contents and length are programmable via the Control port), and
then modulates the TC message.
If the command encoder is modulating a TC message: the new TC message is
modulated back to back at the end of the last one, without any idle inserted (only if the idle
pattern generator is enabled. If the idle pattern generator is disabled, the TCs are
separated by a preamble pattern).
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Safran Data Systems
.
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
Page 133