Grass Valley Switcher Products - Manual (Page 26)

26 Switcher Products — Protocols Manual
Section 1 — Tally Protocol
Message Structure
Messages start with a message code. Message codes are repeated twice in
order to provide positive identification of the message start. Data bytes
could match a valid message code, however the messages have been laid
out such that no two consecutive data bytes have values above 128. Since
all message code characters are above 128, it is not possible for message
data to duplicate the repeated message code.
Communication Specifics
When the switcher begins sending tally information, it will issue an Ini-
tialize command, then send all tally packets as fast as possible. After all
packets have been sent a Data Consistent message is sent.
During idle times (no changes), one background contribution update will
be sent at the frequency specified in
Table 10 followed by a Data Consistent
message. All instances of all message codes are always sent regardless of
which portions of the switcher are currently active.
The source name set is sent one name at a time. All 128 source names are
sent in order and the process repeats.
Background contribution updates and the source name messages are
spaced out and interleaved as shown in
Table 10 . Remaining serial band-
width is used for contribution change updates, if any.
When changes occur, many messages may be required to communicate the
change. At the end of the stream of packets, a Data Consistent message will
be sent. The switcher will insure that data is inconsistent for no longer than
indicated in
Table 10 .
Table 10. Communication Specifics
Category
Field
Rate
Baud Rate
9,600 19,200 38,400 57,600 76,800 115,200
Cycle period (fields)
60 Hz
20 10 5 4 3 2
Background contribution refresh (fields) 260 130 65 52 39 26
Background contribution refresh (sec) 4.329 2.165 1.082 0.866 0.649 0.433
Source name refresh (fields) 853 427 213 171 128 85
Source name refresh (sec) 14.208 7.104 3.552 2.842 2.131 1.421
Max data inconsistent time (sec) 0.333 0.167 0.083 0.067 0.050 0.033
Cycle period (fields) 50 Hz 16 8 4 3 2 2
Background contribution refresh (fields) 208 104 52 39 26 26
Background contribution refresh (sec) 4.160 2.080 1.040 0.780 0.520 0.520
Source name refresh (fields) 683 341 171 128 85 85
Source name refresh (sec) 13.653 6.827 3.413 2.560 1.707 1.707
Max data inconsistent time (sec) 0.320 0.160 0.080 0.060 0.040 0.040