Grass Valley 8921ADT - Manual (Page 49)

8921ADT Instruction Manual 49
Functional Description
The outputs from the gain amplifiers are converted back to a differential
signal before being applied to the A-D converter inputs. The output of the
A-D converter is a serial bit stream which is deserialized into two 24-bit
parallel words in the deserializer block.
A level detection circuit reports when the output is above – 40 dBFS and
near or above clipping on the front panel controls and the web pages.
The multiplexer acts as a 4 x 4 router. Each channel can be routed to any one
of the four channels in the output AES streams with the channel pairing
control.
The output channels from the routing multiplexer are then stored in delay
memory where user-selected delay can be added in increments of 2 msec-
onds.
The channels then enter the gain and AES output section where the audio
processing controls can be used to set the desired output mode such as
inversion, summing etc. The AES 1 and AES 2 gain can be adjusted after
processing has been defined. The channels are serialized and formatted
into an AES stream then sent on to the output drivers.
The output drivers drive either balanced 110 ohm cables or 75 ohm coaxial
cable depending on the selected output format. If no tracking input or
output is required, two unbalanced AES outputs are available on the TRK
IN/AES 1and TRK OUT/AES 2 BNCS.
The reference input uses loop-through BNCs. The AES or AES word clock
and sync from the reference input signal are stripped and the signal is sent
to a genlock circuit that locks 27 MHz to the input. This clock is then used
to generate all internal and AES timing signals.
The microcontroller handles communications with the frame bus and con-
tains the program for controlling and monitoring the module. Switch set-
tings and read and write registers are read by the microcontroller to
perform user adjustments and report status to the user.