Event Counters used for function 11 in MODBUS protocol

I

Thread Starter

Ivar

I am busy implementing MODBUS function 11 (Get Comm Event Counter (Serial Line only)). Handling the function is no problem.

The only question i have is when i have to increase the event counter which is asked by this function.

The specification says....

The event counter is incremented once for each successful message completion. It is not incremented for exception responses, poll commands, or fetch event counter commands.

What is meant by Poll commands? Can someone of you explain this?

Thanks in advance,

Ivar
 
Did you ever get a reply to this, or resolve this? I'm currently in exactly the same position, and Google is not finding anything useful, except this one unanswered post!

Cheers
Stephen
 
Hi,

could you please explain your answer?
I assume you are talking about function codes in hexadecimal representation?!

0x10 => Write Multiple Registers
0x14 => Read File Record

What makes them a poll command?

I would guess that poll commands are initiated by function codes that request values from a device (e.g. "Read ...").
But I doubt the meaning of this concerning the function code 11 :)

There is some more inconsistency in the Modbus Application Protocol Specification v1.1b.
Hopefully there will be a update in future!
 
Hello,

> I assume you are talking about function codes in hexadecimal representation?!

No.

> There is some more inconsistency in the Modbus Application Protocol Specification v1.1b.

Not really; that specification does not cover controllers (PLCs).

Look at other MODBUS specifications.

From: Modicon Modbus Protocol Reference Guide PI–MBUS–300 Rev. J

Function Codes Supported by Controllers
10 Poll 484
14 Poll Controller

The numbers are not in hexadecimal.

Good luck,
Mark
http://peakhmi.com/
 
The same question has also troubled me. And the only clear answer is there. Thank you, Mark!

I didn't look through this Modicon guide earlier, but now I hope it will contribute to my better understanding of MODBUS protocol.
 
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