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4.2 Serial Interface
4.2.1
Interface Configuration
Two user selectable communication protocols are available for this
port STX/ETX (default) or ASCII. Both RS-422/485 (4-wire multi-
drop) and RS-232 serial-communications hardware standards are
supported. The RS-422/485 standard allows communication over
distances as great as 4000 feet (1200 meters) at 9600 baud. RS-232
cable lengths are limited to approximately 50 feet.
In the multi-drop configuration, up to sixteen other addressable
RS-422/485 equipped devices may share the same serial bus.
Termination resistors should be installed on the last device on the
bus. If the bus has multiple runs, the terminating resistor should be
engaged on the last device at the end of each run.
Selection of the serial hardware interface is automatic based on
which pin connections are used for the serial interface cable.
4.3 RF Switch Interface (J5)
On standard units not equipped with optional internal 1 : 1 switch
controller, the RF Switch Interface provides the relay-reported
MPA Hub Mount status and RF inhibit command required by an
external waveguide switch controller as well as two external
interlock inputs. The status relays can be configured for several
purposes, as described below. The only command on this interface,
RF Inhibit, is active at all times and is not subject to the control
mode hierarchy.
The RF Switch Interface is located on connector J5, located on the
MPA Hub Mount front panel. J5 is a 26-pin MS type connector
with pin assignments as shown in Table 4-1.
NOTE: For alternate switch configuration options, Table 4-1 does not
apply. Refer to Appendix G (Hybrid Switch Option) for details.
4-2
E X T E R N A L I N T E R F A C E S
Installation and Operation Manual
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