Communications; Changing Communications; Connecting Rs-232 Communications - Watlow MLS-PM User Manual

Installation

Communications

Changing Communications

Connecting RS-232 Communications

42 MLS User's Guide
The MLS is factory-configured for either RS-232 or RS-485
communications. When you order your unit, specify the type of
communications you need.
• If you use one MLS and you connect it to a computer less than 50
feet away, you can use RS-232 communications.
• If you use more than one computer, or if the computer and controller
are more than 50 feet apart, use RS-485 communications.
PC-compatible computers typically use RS-232 communications. If the
MLS is configured for RS-232 communications, you can connect it
directly to the serial communications connector on an IBM-PC or
compatible computer.
If you use RS-485 communications, attach an optically isolated RS-232/
RS-485 converter to the computer. You can use an internal converter
card or an external plug-in converter.
Follow these instructions to change the unit's communications between
RS-485 and RS-232:
1. Unplug any cables connected to the MLS-PM.
2. If you already installed the MLS-PM in a panel, remove it from the
panel.
3. Unscrew the screws on the PM's casing. (There are either two or four
screws on the sides of the casing. There are two additional screws on
the top of the casing.)
4. Move jumpers JU2, JU4, and JU14 on the upper PC board.
5. If you are changing communications for the last unit on the serial
communications line, also move jumper JU3. Installing this jumper
places a 200 ohm impedance on the line.
6. Reverse instructions 1-3 to reinstall the unit.
The RS-232 interface is a standard phone cable with a 6-pin male phone
connector on one end and a 9- or 25-pin D-sub female connector on the
computer end. (You can order this cable--called an MLS COM cable--
from Watlow-Anafaze. If you order it, specify the length of cable and
the type of D-sub miniature connector you need.)