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D ToD (Time of Day) Protocol Specification
The Time of Day message structure is as shown below (according to G.8271 / Y.1366):
D.1 CCSA ToD protocol Time info message
CCSA is commonly known as "China Mobile" ToD protocol and is supported by a
variety of equipment manufacturers.
ToD message structure CCSA
Description Length expected value
Sync char #1 1 byte 0x43
Sync char #2 1 byte 0x4D
Class 1 byte 0x01
basic type of ToD
message
ID 1 byte 0x20
subtype of each class of
ToD message
Length 2 byte Payload excluding Sync,
length and FCS bytes in
Little Endian Format
Payload n/a
Checksum 1 byte FCs, CRC
CCSA Time info message payload:
Byte
Offset Length Name Value
0 4 Second time of week GPS time of week in second
4 4 Reserve n/a
8 2 Week GPS week (GPS time)
10 1 LeapSecond Leap Seconds (GPS-UTC)
11 1 1PPS status 0x00 Normal* (synchronized to PRTC – time
traceable)
Any value ≠0x00: Not synchronized to PRTC –
time not traceable.
12 1 TAcc Jitter level of 1PPS (0-255):
Not used as not implemented