User Guide

Issue 4, December 2020 Model 780-01/790 User Guide
Page 44 Studio Technologies, Inc.
for Surround
normally connected input signals will be
“locked” to a main timing reference signal
that supports the 48 kHz sampling rate.
But, as an example, a signal associated
with a portable device, while at a 48 kHz
sampling rate, may not be synchronized
(“genlocked”) to the “house” reference.
Connecting this signal to the stereo input
will cause the SRC function to “lock” it to
the Model 780-01’s rate, thus allowing it to
be monitored over a loudspeaker system.
Model 780-01 to Control
Console Connections
Figure 7 gives a detailed description
of the signals that connect the Model
780-01 Central Controller to the one or
more Model 790 or Model 71 Control Con-
soles. The Model 780-01 provides 12 Vdc
for use by the control console’s circuitry.
The DC output is current-limited to 100 mA
to minimize the chance that a short-circuit
condition will damage the Model 780-01’s
circuitry. An asynchronous, bi-directional
data interface links the connected units.
The RS-485 hardware connection scheme
operates at a rate of 115.2 kbit/s and uses
an 8-N-1 data format. The Model 780-01
communicates with each Model 790 and
Model 71 unit 20 times per second, receiv-
ing button and rotary level control informa-
tion and sending LED and 4-digit display
status data.
“Hot” Disconnection of
Control Consoles
There’s no problem relocating one or more
Model 790 or Model 71 Control Consoles
while the StudioComm system is operat-
ing. You can disconnect the 9-pin intercon-
necting cable, move the unit (or units), and
then reconnect without issue. Upon dis-
connection of all control consoles the Mod-
el 780-01 Central Controller will mute the
internal digital audio channels as well as
saving the current operating parameters.
No clicks, pops, or other noises will occur
when the Model 790 or Model 71 units are
again connected. The control consoles
will go through their standard power-up
sequence and then normal operation will
resume.
Channel Status, User, and
Validity Bits
The non-audio bits that are part of the
AES3 digital audio monitor output channel
data are actively controlled by the Model
780-01’s software. The Channel Status
bits use the Professional Use of Channel
Status block. They indicate a word length
of 24 and the current sample rate. The cor-
rect CRC is also calculated and inserted.
The User bits are always set to 0. When
a valid timing reference (sync) source is
recognized by the system the Validity bits
will be set to 1.
The Model 780-01’s hardware is capable
of routing the C/U/V bit information from
any of the L/R inputs, as well as the sync
input, to the main logic device (FPGA)
and then on to the digital audio transmitter
(DIT) integrated circuits. This is provided
for future use and is not active at this time.