Ncs Cc/Ces Tdm Channel - Furuno FELCOM 12 Service Manual

1. NCS CC/CES TDM Channel

The NCS common channel and CES TDM channels share a common overall structure.
The TDM channels are based on fixed-length frames of 10368 symbols tarnsmitted at
1200 symbols/s giving a frame time of 8.64S. 10,000 frames are transmitted every day
(8.64s x 10000= 24 hours).
Each frame carries a 639 byte information field, followed by a flush byte (all 0s).
The first packet in the information field is always the Bulletin Board (BB) packet.
The bulletin board contains information on the network configuration and the correct
frame number.
TDM Frame
Frame Format
8 7 6 5 4 3 2 1
1
Bulltin Board Packet
14
Signalling Channel
Descriptor Packet
Message
or Signlling Packet
640
8.64sec (10368 TDM symbols)
TDM Frame
0
Channel
0
A C D S L A
Figure 2-2
2-2
TDM Frame
8 7 6 5 4 3 2 1
Type Length 1
Network Version
Frame Number
2-F
Sig Channel
E Spare
Count
Spare
Local
Origin ID
Status
Services
Rnd Interval
Check sum
14
8 7 6 5 4 3 2 1
Type Length
1
E Spare
Satellite Freq. Code
×
28 2bit
Slot
State
Markers
Check sum
13
Packet descriptor
0 (gero) when in
CES TDM
Frame descriptor
TDM descriptor
Service descriptor
Randomizing Interval
Packet descriptor
Indicating the channel of the
signalling channel