Comtec CDM-840 - ECM Message Processing

CDM-840 Remote Router MN-CDM840
Appendix G Revision 3
G–5
G.1.3 CDM-840 ECM Message Processing
Figure G-2 illustrates the internal logic diagram of the remote processing registration message.
Processing
Segment
Description Remarks Action Remarks
1 ALOHA
“Not Registered” or
“Reverted”
A
Random registration attempts with backoff
until in TAP
2 REGISTRATION B In TAP
3 SWITCH PENDING C Complete the registration protocol
4 SWITCHED D Not in TAP
E
Registration complete – no more Slots
needed
F
Received “Switch Command” message
from VMS
G Received “Revert” message from VMS
Figure G-2. ECM Message Processing – CDM-840 Remote Router
• The CDM-840s are configured to receive the outbound carrier and are given a TAP (Group)
identifier number (default 1) that sets the internal filtering if multiple TAPs are used.
• Upon receipt of the TAP message, the CDM-840 sets modem transmission parameters (if
required), initializes timing, and picks at random an SAS to start entry by sending a probe
(slot transmission).
• The CDM-840, based on its current ECM state, either requests an assigned slot or waits to
be switched:
o An assigned slot request indicates to the HCC if the CDM-840 has more data (e.g.
registration protocol) to send.
o A switch request indicates that the CDM-840 is requesting dSCPC bandwidth. These two
flags are independent.