Issue:
Looking for a way to monitor the communication status between a Magelis HMI and the PLC.

Product Line:
Vijeo Desginer (all versions), Magelis HMI (all HMI series programmed with Vijeo Designer)

Resolution:
There are a collection of statistic variables that can be used to monitor the communication between a Magelis HMI and a PLC using any driver (serial or ethernet) supported by Vijeo Designer. Here is a table describing those statistics:

Current Statistics (@stat) and Previous Statistics (@prevstat)

The driver collects the current and previous statistics listed in the following table. In the variable's Device Address field, use @stat or @prevstat to identify whether you want to view the current statistics or previous statistics, then type a colon and the index number.

Examples:

@stat:2 = Total Count

@prevstat:8 = Initialization Failed

For details on how to set up variables so you can display driver statistics, see Section 5.3.1, Creating Variables to Display Driver Statistics from help

Index	Name	Description
0	Total Good	Received without error.
1	Total Bad	The total number of errors of all types.
2	Total Count	Total Good + Total Bad.
3	No Reply	No reply was received in response to the request.
4	Checksum Failed	Received a request or response*1 with an incorrect checksum.
5	Wrong Address	Received a request or response*1 with an incorrect address.
6	Error Response	Received an error response from the equipment.
7	Invalid Response	Received a response that contained a protocol error.
8	Initialization Failed	Failed to initialize communications with the equipment.
9	Write Failed	Failed to write a new value to the equipment.
10	Internal Error	Internal driver error indicates improper driver configuration or driver failure.
11	Transmit Failed	Failed to transmit a request or response*1.
12	Unsupported Request	Received a request for an unsupported service.
13	Invalid Request	Received a request that contained a protocol error.

*1 Client-type drivers send out requests and receive responses. Server-type drivers receive requests and send responses.

• Driver statistics are read-only. You cannot use the Keypad to reset or change driver statistic values.

• Driver statistics are reset to zero when you turn off the target machine or when you roll over statistics. See Section 5.3.3, Rolling Over Driver Statistics from help

• If a driver statistic variable reaches the maximum value for a 32-bit integer (2,147,483,647) and still continues to collect statistics, it will overflow to a negative number. Reset driver statistic variables before they overflow and have negative values. For example, at a rate of 100 packets per second, the Total Count counter overflows in about 248 days. To make sure the driver statistics do not overflow, you can set up a periodic script that rolls over the driver statistics and runs once a month.

• The driver collects all the current and previous statistics listed in the above table, even if there are no variables associated with driver statistics.

For details on how to set up variables so you can display driver statistics, see Section 5.3.1 of the Online Help, "Creating Variables to Display Driver Statistics."

To utilize these statistic variables, simply create an External variable assigned to your Modbus RTU equipment and assign the device address @stat:0 for Total good packets or @stat:1 for Total bad packets. There are other statistics that you could monitor to check for good/bad communication as the table indicates.

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