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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
