Installation
8LS User’s Guide 35
RS-485 Connections
Connection of Watlow Anafaze controllers to a system computer
requires an interface at the computer to convert RS-232 levels to RS-
485. Watlow Anafaze recommends two options:
•
B&B Electronics 485OIC with 485PS2 or 485OISPR with 485PS.
•
Black Box Model LD485A. The LD485A should be configured for
DCE operation, with the RTS/CTS delay jumper in the "on" posi-
tion. Watlow Anafaze can supply this converter configured and
checked out with the system on request.
Jumper setup for the B&B Electronics:
1. JP1 Off
2. JP2
Installed
Normal Operation LD485A installation setup:
1. DCE operation (Dip shunt in XW1A socket)
2. Normal operation (Front panel switch out)
3. Full Duplex operation (Jumper W8 on Full)
4. RTS/CTS Delay set to ON (Jumper W9 to ON)
5. Unterminated operation (Switch S2 to Unterm)
6. No jumper at position W7
The RS-485 specification is for "balanced line" operation, and is not
true differential. Thus a common connection is required between all
stations on the communication line. This can be accomplished by either
a 5th wire (which could be shield) or a common ground connection.
The Watlow Anafaze system more conveniently supports the common
ground connection, although 5th wire can be supported if required due
to common mode voltages generated in a given installation. The 3rd
wire connection would be required only if the "common mode" voltage
between stations exceeds the RS-485 specification of 7 volts peak.
To make sure the communication system works, the controller chassis
must be electrically tied to Earth ground, and the host computer
communication must be tied to Earth ground. If the host computer RS-
232 communication is not referenced to Earth ground, install the 100
Ω
resistor in W7 as recommended by Black Box.
The following diagram shows the recommended system hookup. The
transmitter from the host computer connects in parallel to the controller
receivers, and the host computer receiver connects in parallel to the
controller transmitters. A single "daisy chain" is recommended. Octopus
connections or "spurs" are discouraged.
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