Specifications

Gaia
GAIA.ASU.SP.ESM.00007
Issue 2.00
Page 52 of 79
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GAIA.ASU.SP.ESM.00007 (Avionics SCOE Req Iss 2).doc
3.7.2 SCET/HREF Interface
AVI-3369/CREATED/T
SCET/H
REF
data pairs (as defined in Section 3.5.4) shall be transferred to the CCS for SCET/UTC
correlation every PPS.
AVI-3370/CREATED/T
The data pairs shall be transferred to the CCS in network byte order using the message format
defined in Figure 3.7-1.
Message Type = 1 Message Length = 16
31……………….…………......………16 15……………...………...………………0
SCET (seconds)
SCET (sub- seconds) - 24 BITS
Reference Time High
Reference Time Low
Not used
Data Word 0
Data Word 1
Data Word 2
Data Word 3
Data Word 4
Header
where:
• Data Word 0 is the message header comprising the Message Type (MS 16 BITS) set to
a value of 1, and the Message Length (LS 16 BITS), set to 16.
• Data Word 1 contains the MS 32 BITS of the SCET (corresponding to the seconds
component)
• Data Word 2 (lower 3 bytes) contains the LS 24 BITS of the SCET (corresponding to
the sub-second component)
•
Data Word 3 contains the MS 32 BITS of H
REF
•
Data Word 4 contains the LS 32 BITS of H
REF
Note: H
REF
comprises a 64 BIT Integer equivalent to the number of microseconds since the
beginning of the current year.
Figure 3.7-1: SCET/H
REF
Data Transfer Format