Grass Valley Switcher Products - Manual (Page 106)

106 Switcher Products — Protocols Manual
Section 4 — DPM CPL Protocol
Note The switcher relies on the key half of an aux bus pair to be connected to the
same transforming channel as its video half. This interface makes no provi-
sion for use of the key side of a switcher’s aux bus to feed a second video
channel. While basic functionality can be achieved in this mode, functions
such as effects send, front/back switching and tally will not function properly.
Grass Valley Group accepts no responsibility for interfaces which do not
adhere to this constraint.
• The term “Tally,” as used here, means that the switcher can receive a
message from the DPM indicating whether the DPM is on-screen or not,
and the switcher can use this information to tally sources feeding the
DPM, providing proper panel and camera tally.
Note The DPM informs the switcher whether or not its image is on screen without
regard to whether the DPM itself is on air. The switcher computes the on-air
tally based on the on/off screen information and whether or not the DPM
output is on air.
• Distinguishing between the terms “source” and “input”: “Source map-
ping” provides a level of indirection between the switcher’s physical
inputs and a source selection panel button. Input 20 could be mapped
to button 1. “Input” would then refer to the physical entity, and
“source” to the button and to what is stored as part of the switcher’s
effect.
Source information exchanged with the DPM is the logical “source” form
of the information that is used—not the physical input. The switcher trans-
lates this internally to a physical input.
Note The term “crosspoint” can be misleading, meaning both source and input at
different times. In this documentation, the term crosspoint refers to the
actual switching matrix used in routing signals.
Switcher Configuration
In order for this interface to function as expected, the switcher must be con-
figured properly. Configuration details are covered in the separate Installa-
tion and Service Manual of the switcher model involved.
General Protocol Notes
The protocol used for this interface is designed around setting values and
receiving status (values). A subscription mechanism provides for status
updates when changes occur providing more timely delivery of informa-
tion without constant and frequent polling.