Frame Verification; Telemetry Frames Or Raw Data; Telemetry Data Time-Tagging - Safran CORTEX CRT Quantum User Manual

Frame Verification

3.3.9.
Reconstructed frames will be verified only if parameter Frame Checking is set to CRC or Checksum.
The CRC is user-programmable via two parameters: CRC Polynomial (CRC16, CCITT, etc...) and CRC Preset
Value (usually all bits set to 0 or to 1).
The checksum value is supposed to be the last byte of each frame. The CRC Preset Value is added to the
computed checksum: if the frame checksum does not include the synchronization word, enter the one's
complement of the synchronization word in the CRC Preset Value.
The CRC and Check Sum algorithms may include or not include the synchronization word depending on the
registry setting (See section 4.2.8.3.5).

3.3.10. Telemetry Frames or Raw Data

When the Frame Synchronizer is ON, reconstructed frames are time-tagged and transmitted to the Telemetry
Clients. The telemetry message size is determined by the minor frame size (IRIG format), or the transfer frame
size (CCSDS format).
When the Frame Synchronizer is OFF, telemetry data from the Bit Synchronizer are stored into programmable
fixed-length messages that are time-tagged and then transmitted to the Telemetry Clients. The telemetry
message size is determined by the block size.

3.3.11. Telemetry Data Time-Tagging

The time-tag in each telemetry message transmitted to the Telemetry Clients corresponds to the reception of the
last bit, rising edge (if the telemetry time-tagging flag is set to 0 in the Windows registry) or first bit, rising edge
(if the flag is set to 1) of the telemetry frame (Frame Synchronizer ON) or the telemetry block (Frame
Synchronizer OFF). Note: the first bit of the telemetry frame is the first bit of the Synchronization Word. Default
time-tagging flag is « Last bit ». The time-tag accuracy (provided that the selected time-tag coding is Code 2 –
Refer to the MCS User's Manual and to the TCP-IP Interface Specification) is within ±50µs (without external 1-
PPS) or ±100ns (with external 1-PPS) of the reference time supplied to the CORTEX CRT Quantum.
© Safran Data Systems
COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
This document is the property of
It cannot be duplicated or distributed without expressed written consent.
Safran Data Systems
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Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
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