MKS Granville-Phillips 358 series, Instruction Manual

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Chapter 8
114
Series 358 Micro-Ion Controller Instruction Manual - 358013 - Rev. B
8.9 RS-485 Troubleshooting
The first thing to do if trouble arises is check the following configuration
options:
1. Check the switching settings.
Be sure the baud rate, character format and framing, and interface
protocol are matched to your host computer or terminal's
requirements. Note that there may be several mismatched parameters.
2. Check the command format.
Be sure the strings you output to the controller are in accord with the
syntax defined in
Preparing to Use RS-485 Computer Interface on
page 90.
Table 8-6 RS-485 Troubleshooting Guide
Symptom Possible Cause
Microcontroller reset LED CR1 is
illuminated or flashing Microcontroller failure
No response or garbled output Baud rate incorrect. Character length incorrect or stop bit(s) incorrect
Bad cable
Responds intermittently Poor cable connections, ground fluctuations (the maximum common mode
potential across the system is 7V) and EMI from other sources.
The terminating resistor circuit is not installed, or is improperly installed.
If the start character is not received properly, the controller may not interpret it as
a start character and the controller will not respond. The Host software must be
prepared to re-send a command if a response is not generated within a reasonable
period of time.
OVERRUN ERROR message Stop bit(s) incorrect, host software failure
PARITY ERROR message Parity incorrect
SYNTAX ERROR message Message to controller not in accord with specified syntax