Init/online – Grass Valley Switcher Products User Manual
Page 108
108
Switcher Products — Protocols Manual
Section 4 — DPM CPL Protocol
Init/Online
This section describes the sequence used on start up communications. A
DPM must respond and perform the indicated steps in order to achieve a
reliable connection with the switcher.
If the Switcher is reset, or its DPM port configuration is changed:
1.
The switcher sends out the message:
SEND_EVENT, EID_ONLINE (15)
This tells the DPM that the switcher just came on-line.
2.
The DPM acknowledges this message with the RETURN_CODE
message echoing the return ID from the switcher’s SEND_EVENT
message:
val = OK (0). (The switcher ignores the return value.)
3.
The switcher then requests the DPM system name (by subscribing to it):
SUBSCRIBE, IMMEDIATE, PID_SYSTEM_NAME
4.
The DPM sends its name:
ISSUE, PARAMETER_ARTICLE, PID_SYSTEM_NAME
5.
Once the switcher receives the system name message (can be any name
text) the switcher sends subscription messages for all of the parameters
listed below Appendix B.
Note
Other subscriptions may be solicited as well, but may be safely ignored. Their
status is used only for Krystal and Kaleidoscope interfaces.
6.
The DPM returns ISSUE messages containing the values for all of the
subscribed parameters. From then on, any changes to any of these
parameters will result in new issue messages being sent to the switcher.
Note
The switcher does not poll for changes. It relies on the subscriptions regis-
tered during initialization to provide it with timely updates to parametric
changes.
If the DPM is reset or its switcher interface is reconfigured, the sequence is:
1.
The DPM sends out the message:
SEND_EVENT, event EID_ONLINE
This tells the switcher that the DPM just came on-line.
2.
The switcher acknowledges receiving the on-line message by sending
the RETURN_CODE message:
(the message header’s return ID is set to 0)
val = EID_ONLINE (15).
then sends out a message cancelling all subscriptions:
UNSUBSCRIBE, CLEAR_SUBSCRIPTIONS
3.
The switcher then takes over the initialization process with step 3
above.