Watlow CAS - Manual (Page 81)

Troubleshooting
CAS User’s Guide 71
Checking Computer Supervised Systems
Four elements must work properly in a computer supervised system that
uses an IBM-compatible computer and ANASCAN:
• The CAS.
• The computer and its RS-232 or RS-485 serial interface.
• The RS-232 or RS-485 communications line.
• The computer's software.
For CAS troubleshooting, disconnect the communications line from the
computer before you follow the troubleshooting steps explained in the
previous sections. Troubleshooting for the computer and
communications are explained in the sections below.
Computer Problems
If you are having computer or serial interface problems, check the
following:
1. Make sure you are using DOS 5.0 or a later version of DOS.
2. Check the communications interface, cables, and connections.
Make sure the serial interface is set according to the manufacturer's
instructions.
• To test an RS-232 interface, buy an RS-232 troubleshooter from
Radio Shack or an equivalent supplier. Attach the trouble-
shooter between the CAS and the computer. When
ANASCAN sends data to the CAS, the troubleshooter's TX
LED should blink. When ANASCAN receives data from the
CAS, the RX LED should blink.
• You can also connect an oscilloscope to the transmit or receive
line to see whether data is being sent or received. If the serial
interface does not function, contact your computer service
representative.
NOTE
Most communications problems are due to incorrect wiring or from
incorrectly setting the communication parameters. Therefore, check
the wiring and communications settings first.
If you have more than one CAS, or you are using more than 50 feet of
communications wiring, you must use RS-485 communications.
Otherwise, you can use RS-232 communications. The CAS is
configured for RS-232 communications when it is shipped. If you are
using RS-485 communications, you must set the internal RS232/RS485
selection jumpers to the correct position. (See Installation, for
information about changing jumpers.)