Multi-Drop Network - Ten-Tec RX-340 Technical Manual

CHAPTER 5
DETAILED REMOTE RS-232 OPERATING INSTRUCTIONS

5-1 MULTI-DROP NETWORK:

In addition to front-panel control, the RX-340 may be controlled remotely via its
MULTI-DROP RS-232 interface using a PC (Personal Computer). The RX-340 must be
in Local mode for front-panel operation and Remote mode for RS-232 control. See
section (5-10) for details of the Remote button and the RS-232 security commands.
Control software is necessary for remote operation. The RX-340 interface is based on
plain text (ASCII) codes and strings which reduces the software design burden. An
ASCII based interface allows the operator to exercise the RX-340 using a dedicated
terminal or through a PC running, terminal-emulation software. In this way, software
designers can quickly become familiar with commands and responses of the RX-340.
The RX-340 operates as a DCE device for serial interface applications, and a 3-wire
interface is required for connection to a suitable controller (TXDATA, RXDATA and
GND). When connecting multiple RX-340s to a single controller, all units are wired
parallel to the control bus. In this way, all receivers share a single TXDATA line,
RXDATA line and GND line (See figure 5-1). After the receivers have been wired, they
must be configured. Dipswitches S1 and S2 located on the rear panel allow users to set
serial interface parameters and receiver addresses. Dip switch S1 is used to select serial
interface parameters (See figure 5-2). Dip switch S2 is used to set the receivers address
(range 0 to 127). Switch S2-1 is not used for address selection and should be left in the
down position for normal operation. (This switch is used to activate Non-Multi-drop RS-
232 default).
The RX-340 is interfaced to a PC or other suitable controller via a Multi-drop serial
network. Signal levels for the network are RS-232 compatible. However, unlike
conventional RS-232 systems which allow only a single connection, the RX-340 has been
designed to allow multiple connections. While any number of receivers may be
interconnected at one time, the number of simultaneous connections is limited by line
capacitance. Total capacitance should not exceed 2500 pF. However, the Baud rate and
RS-232 drive delay may be adjusted to allow operation with a less than perfect
installation (See section 5-4, Hnnn command).
The multi-drop feature may be disabled by sending the 'US' command. After this
command is received, the interface becomes standard RS-232C (single receiver system).
The 'U4' command restores the multi- drop feature. Set dip switch S2-1 to configure the
power-up default of the Multi-drop feature (See figure 5-2).
Important Note: A standard serial cable will not work. An interface cable for the RX-
340 must use pins 2, 3 and 7 only. Other pins on the DB-25 connector carry DSP data.
5-1