GRASS VALLEY PERFORMER, Instruction Manual

Page: 156 / 182

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Section 3 —
Operation & Service
TEN–20/20–TEN Serial Interface Protocol
ASCII protocol is used between the Serial Interface and a
controlling terminal or computer. Baud rate, parity, stop and data
bits are determined by Serial Interface switch settings and the
limitations of the terminal or computer used. These items are
described in the Installation section of this manual.
NOTE:
This protocol works ONLY between the TEN–20/
20–TEN SERIM Serial Interface and a user supplied computer. It
IS NOT a Performer protocol.
All valid messages received by the serial interface will initiate a
response. The response will begin within 1.0 second of the receipt
of the last byte of the original message. The Serial Interface is
silent unless it receives a valid message. Thus, if another controller
changes routing switcher configuration, you must request current
status to discover the change as the Serial Interface will not initiate
a report. The computer should not send messages unless a
response to the previous message has been received or the 1.0
second time interval has expired.
Each message must begin with a unique header and terminate
with a line feed. System configuration (number of levels enabled)
does not affect message length. Disabled levels, or levels which
you do not wish to switch (breakaway) should be sent as 00.
A checksum is included in all messages. The checksum is the sum
of all preceding bytes of the message including the header,
module 256. This sum is split into a high and low nibble and
transmitted as 2 bytes. Each nibble has a range from 0 to F Hex.
Each nibble is transmitted as its ASCII equivalent (30-39 and 41-46
Hex). See the ASCII table at the beginning of the Protocol
descriptions.