Communication Driver Log-Enabled Variables

All of the standard drivers have 7 variables that may be logged. When recorded in a report, these allow you to monitor driver communications over time to spot problems or ensure that response times are acceptable.

Logged Variable

Description

1. ErrorValue

An error value or code associated with a driver's communication error.

2. FailedCount

Incremented on each communication error.

3. FailedRetryCount

Incremented if failure occurs on a retry. Drivers will usually retry more than once before designating an error to be an "error on retry". Thus, this count will always be less than or equal to the FailedCount.

4. SuccessCount

Count for successful reads and writes, incremented on each successful operation.

5. Quality A mathematically derived indication of communication error rates. Used to show the driver's overall "health". (1)

6. ResponseTime

The time it takes the PLC/RTU to receive a command, process it and send a response. (2)

7. ErrorAddress

If an address was associated with the error, it will be recorded here.

A publicly accessible variable, CommStatsTimeStamp, holds the most recent timestamp that was used to update these variables and write them to a DAT file.

Monitoring Driver Health and Errors

To view errors, use the Reports Page. Two reports are standard for all communications drivers. The Driver Communication Error Detail Report and the Driver Communication Summary Report. Both are described in "Reports Page: Types of Reports".

You can also place the appropriate Show Statistics Button Widget on a page to monitor the values in real-time.

On a busy system, it is dangerous to use these properties in expressions. SuccessCount and FailedCount in particular update with every read. Excessive RPC traffic may result, slowing your overall system performance.