Grass Valley XSwitch Feb 08 2006 - Manual (Page 31)

XSWITCH Installation and Operation Manual 31
Appendix
A
Remote Activation
The XSWITCH™ has remote activation capabilities. The following infor-
mation is a communication guide to assist with use of this functionality.
Connector and pinout information is also supplied. Grass Valley does not
offer a remote activation device. This device must be supplied by the cus-
tomer.
A standard bus communication consists of a command sent by an origi-
nating device to a receiving device with the receiving device returning a
reply. If the reply is not received within a designated time period, then the
originating device has the option to retry or cancel the command.
Hardware Specifications
The computer may listen, talk, or interrupt bus comms at any time. The
active lines to the RS-232 port are TXD, RXD, and ground, as shown in the
Installation Manual. No hardware handshaking is used. The RS-232 port
signal levels are +12 and -12 volts.
Care must be taken to insure that the electrical connections are of the correct
polarity and voltage, or damage may result. Be sure to consult the partic-
ular device connector diagrams for correct signal pinouts and polarities.
Bus Packet Format
Grass Valley communication packets consist of 10-bit words containing 1
start bit, 8 data bits, and 1 stop bit. The words are transmitted one bit at a
time (serially), least-significant bit first. The data rate is fixed at 9600 baud.
Successive words in a packet must follow one another within 20 millisec-
onds or the packet is declared invalid. There must be a minimum delay of
40 milliseconds between successive packets. Any computer connected to
the communication bus must adhere to these packet specifications. The bus
comms are half-duplex.