Comtech EF Data CDM-840 - Manual (Page 229)

CDM-840 Remote Router Revision 2
Appendix F MN-CDM840
F–9
F.3 ECM Operational Scenarios
F.3.1 Scenario 1 – VMS Initial Registration Process
For proper registration with the VMS, initialization (power-up and bootup) of the ECM-enabled
CDM-840 is required.
Upon initialization, the CDM-840:
1. Receives a VMS Announcement, sets up an active VMS IP Address, and initializes ECM
TAP processing;
2. Transmits a registration request using a selected SAS, and sets a “Needs Slot” flag in the
RID message;
3. Receives the HCC response, through the TAP, assigning an SRS;
4. Continues to transmit the registration request message in SRS;
5. Receives registration from the VMS (Standard Processing);
6. Transmits a registration acknowledgement to the VMS in SRS – it signals the HCC by
clearing “Needs Slot” and sets the “Registered with VMS” and “Need to be Switched”
flags in the RID message.
7. Receives the HCC response, through the TAP, as an acknowledgement – the HCC then
clears the SRS allocation and sends ECM switch requests to the VMS on behalf of the
CDM-840 (Standard Processing);
8. Waits for VMS dSCPC assignment (Standard Processing).
F.3.2 Scenario 2 – Reverted or Auto-Recovered Messages
“Revert” or “Auto Recover” of an already registered CDM-840 is required when:
• The CDM-840 was forced into or dropped back to ECM mode;
• The CDM-840 transmits into an SAS setting due to a “Need to be Switched” flag in the
RID message;
• The HCC sends ECM switch requests to the VMS on behalf of the CDM-840 (Standard
Processing).
F.3.2.1 ECM Revert Cycle Timing
When a CDM-840 reverts from dSCPC to ECM, there is typically no wait because the CDM-840 is
always monitoring TAP cycles to synchronize. It then randomly selects a slot in the next cycle