GRASS VALLEY PERFORMER, Instruction Manual

Page: 26 / 182

1-6
Section 1 —
Product Description
VAA Board
The VAA board contains:
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Video processing circuitry
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Audio processing circuitry
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Control circuitry
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Parameter-determining switches
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Vertical Interval Strobe generating circuitry
Performer video processing circuitry consists of: ASIC cable
equalizers, an ASIC serial crosspoint, and an ECL line driver.
Serial bit stream at inputs is converted to parallel, and processed
in parallel digital domain, to extract line ID information and to
generate the vertical interval switching strobe.
The Performer supports two independent audio AES/EBU
channels (AUDIO 1/2 and AUDIO 3/4). Inputs can be either
balanced or unbalanced. Audio is received and converted to TTL
signals by RS485 line receiver circuitry. A pair of 8X1 multiplexers
form a 10X1 multiplexer to select one of the ten input signals of
AES Ch 1/2 to the output. AES Ch 3/4 uses identical circuitry.
Control circuitry is based on an 68HC711 CPU running at
4.9152MHz, supported by a 27C256 PROM and a DS1225AD
RAM. The CPU contains a programmable, full-duplex, serial
channel to handle serial data to and from the RS232, RS422, and
RS485 driver and receiver circuits. Three 8-segment switches
allow users to determine serial baud rate, communications
protocol, external or internal VI strobe, and other functions. The
internal VI strobe is stripped from digital video by a TRS ID Data
Separator. An external VI strobe may be used if desired.
Front Panel Board
The Front Panel board mounts a row of 13 buttons and three, two-
character, seven-segment displays. The buttons are sequentially
scanned by the VAA board microcomputer (Switch Write); a
pressed button is detected by one of the two Switch Read lines and
the appropriate source taken to the output of the switcher. The
take may be Audio Follow Video or breakaway depending upon