Grass Valley 2200 - Manual (Page 96)

5-6
Section 5 Ñ Digital Effects Interface
NOTE: The last packet containing real time messages sent by the DPM in
a field must complete transmission 3 milliseconds before the end of the
field. (13.6 mS from the start of the Þeld for 525/60 or 22 mS for 625/50.) No real
time messages should be sent to the switcher during this end-of-Þeld period.
Transmissions during this time can disturb critical processes within the switcher
and cause the program video output of the switcher to glitch randomly.
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 conÞguration 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 switcherÕs 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
registered during initialization to provide it with timely updates to parametric
changes.