Experimental Physics and
Industrial Control System

Mark Rivers <[email protected]> · Wed, 2 Sep 2015 14:46:41 +0000

Hi Christophe,

Here are some things to look for:

- On vxWorks perhaps a task has been suspended.  Issue the "i" command to look at the status of all of the tasks.

- Perhaps there is a deadlock.  Issue this command several times in a row to see if there is a mutex that is always locked:
epicsMutexShowAll 1

- Perhaps there was a stack overflow.  Issue this command and look for tasks with a margin of 0
checkStack

If you don't find anything there then send us the output of "asynReport 10" on the Read port and Write port.

Mark

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of haquin
Sent: Wednesday, September 02, 2015 9:00 AM
To: tech-talk
Subject: Asyn ModbusTCP communication KO without error messages

Hi all,

I have a VxWorks IOC (with MVME-CPU using both eth interfaces) communicating with a siemens S7PLC via Asyn/ModbusTCP.
EPICS release 3.14.12.4 Asyn v4.22

After a while  (1 or 2 days), the communication is not working anymore ... but I have no error messages (no timeout nor 
disconnection ...).
 From IOC side I a have "Read Multiple Register" function reading the whole modbus table (109 registers) every second
and a "Write Multiple Register" function writing the value of a counter incremented every seconds from record level.

When I activate AsynTrace on IP Port or Read or Write ports there is no messages ...
asynReport on Read port indicates only 1 Read OK
asynReport on Write port indicates 0 Write OK

I can read the PLC register via "modpoll" tool from a Linux PC
I can start a Linux IOC connected to the same PLC
The netstat command on IOC shell tells that the TCP port is established but the Recv-Q is not equal to 0 (12 for example)

What can explain this behavior ?

thanks in advance !

-- 
Christophe Haquin
Control and Real Time systems Engineer

+33 231454661 office
+33 231454728 fax
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System