Studio Technologies 76DA V.4.12 - Manual (Page 49)

Model 76DA/77 User Guide Issue 9, May 2014
Studio Technologies, Inc. Page 49
for Surround
output can be connected to other devices
that find need for the now-synchronized
signal. In some cases it may be useful to
connect the stereo input C direct monitor
output to the input of a signal router, allow-
ing an entire facility to access the signal.
Model 76DA to Control
Console Connections
Figure 7 gives a detailed description of the
signals that connect the Model 76DA Cen-
tral Controller to the one or more Model 77
or Model 71 Control Consoles. The Model
76DA provides 12 volts DC for use by the
control console’s circuitry. The DC output is
current-limited to minimize the chance that
a short-circuit condition will damage the
Model 76DA’s circuitry. An asynchronous,
bi-directional data interface links the con-
nected units. The RS-485 hardware con-
nection scheme operates at a rate of 115.2
kbit/s and uses an 8-N-1 data format. The
Model 76DA communicates with each
Model 77 and Model 71 unit 20 times per
second, receiving button and rotary level
control information and sending LED and
4-digit display status data.
“Hot” Disconnection of
Control Consoles
There’s no problem relocating one or
more Model 77 or Model 71 Control
Consoles while the StudioComm system
is operating. You can disconnect the 9-pin
interconnecting cable, move the unit (or
units), and then reconnect without issue.
Upon disconnection of all control consoles
the Model 76DA 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 77 or
Model 71 units are again connected. The
control consoles will go through their stan-
dard 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
76DA’s software. The Channel Status bits
use the Professional Use of Channel Sta-
tus block. They indicate a word length of 24
and the current sample rate. The correct
CRC is also calculated and inserted. The
User bits are always set to 0. When a valid
timing reference (sync) source is recog-
nized by the system the Validity bits will be
set to 1.
The Model 76DA’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) in-
tegrated circuits. This is provided for future
use and is not active at this time.