10. Series 8 I/O
Troubleshooting
10.3. Communication problems
R500
Series 8 I/O User's Guide
257
April 2017
Honeywell
There are application specific diagnostic routines that run during the normal
operation which normally runs at a higher rate and priority. Examples of application
specific diagnostics are:
Checking the integrity of calibration data
Redundancy diagnostics in redundantly configured modules
Reference voltage tests in analog modules
Short circuit detection in Digital Output modules
10.3 Communication problems
IOLINK - loss of communications
IOMs can experience a loss of communication with the IOLINK function block for
several reasons. The two most common reasons are:
the C300 losing power, or
a fault in the IOLINK cable
Whenever an IOM can no longer communicate with a C300, the channels contained
within the IOM use the following:
FAULT parameters
FAULTOPT, and
FAULTVALUE
and a separate IOM internal fail-safe timeout to ensure that the channel is in the
appropriate fail-safe setting.
IOLINK - re-establishing communications
Once communication between a C300 and an IOM is re-established, the C300 determines
if the databases between the C300 and IOM are identical. If they are different and the
IOM's DBVALID flag is true, (indicating that the IOM configuration has been
maintained through the period of loss of communication), then the C300 uploads the
configuration from the IOM.
If the IOM's DBVALID is false (indicating the IOM configuration is not maintained
through the period of communication) and if C300 has a copy of last valid IOM
configuration, then the C300 downloads the configuration to the IOM.