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<== Date ==> <== Thread ==>

Subject: RE: Modbus disconnecting
From: Mark Rivers <[email protected]>
To: Alex Wallace <[email protected]>, "[email protected]" <[email protected]>
Date: Sat, 11 Jan 2014 03:48:46 +0000
Hi Alex,

I don't think the Modbus ports are really losing their connection to the IOC.  Rather some message are not receiving a reply within the timeout period.

Is this the complete set of messages over that ~3 hour time period?  If so then It looks like the timeouts are quite intermittent, fewer than 10 per hour.  It looks like you have set a 2 second timeout on your Modbus port drivers?

This could be due to network traffic or hardware problems causing dropped packets that are not recovered before the 2 second timeout.  

You could try increasing your timeouts to 5 seconds and see if the frequency of timeouts decreases.

Mark

______________________________________it
From: [email protected] [[email protected]] on behalf of Alex Wallace [[email protected]]
Sent: Friday, January 10, 2014 7:35 PM
To: [email protected]
Subject: Modbus disconnecting

Hi,

I know this is a fairly vague problem, but I figured I'd ask to see if
there are somethings I might not be thinking of. We've recently had a
problem where some of my modbus ports lose their connection to the PLC.
Currently running 2.4.0 of Mark River's modbus module. Nothing has
changed in the configuration and this has been working for a long period
of time. Here's what we get from the IOC log:

[Jan 09 12:32:47] 2014/01/09 12:32:47.157 drvModbusAsyn::doModbusIO port
K2_Yn_Out_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502
timeout: Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 12:58:21] 2014/01/09 12:58:21.098 drvModbusAsyn::doModbusIO port
XPP_Yn_Out_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 12:58:22] 2014/01/09 12:58:22.547 drvModbusAsyn::doModbusIO port
K2_Yn_Out_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502
timeout: Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 12:58:23] 2014/01/09 12:58:23.198 drvModbusAsyn::doModbusIO port
XPP_Cn_In_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 12:58:25] 2014/01/09 12:58:25.547 drvModbusAsyn::doModbusIO port
K2_Cn_In_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502
timeout: Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:13:52] 2014/01/09 15:13:52.351 drvModbusAsyn::doModbusIO port
XPP_Xn_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:13:54] 2014/01/09 15:13:54.051 drvModbusAsyn::doModbusIO port
K2_Xn_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:13:54] 2014/01/09 15:13:54.452 drvModbusAsyn::doModbusIO port
XPP_Yn_Out_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:13:56] 2014/01/09 15:13:56.552 drvModbusAsyn::doModbusIO port
XPP_Cn_In_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:14:01] 2014/01/09 15:14:01.414 drvModbusAsyn::doModbusIO port
XPP_Yn_Out_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:14:02] 2014/01/09 15:14:02.046 drvModbusAsyn::doModbusIO port
K2_Yn_Out_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502
timeout: Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:14:05] 2014/01/09 15:14:05.046 drvModbusAsyn::doModbusIO port
K2_Cn_In_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502
timeout: Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:14:11] 2014/01/09 15:14:11.369 drvModbusAsyn::doModbusIO port
XPP_Xn_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:14:13] 2014/01/09 15:14:13.048 drvModbusAsyn::doModbusIO port
K2_Cn_In_Bit error calling writeRead, error=plc-xpp-lss.pcdsn:502
timeout: Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:16:07] 2014/01/09 15:16:07.250 drvModbusAsyn::doModbusIO port
XPP_Yn_Out_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:16:09] 2014/01/09 15:16:09.351 drvModbusAsyn::doModbusIO port
XPP_Cn_In_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0
[Jan 09 15:16:11] 2014/01/09 15:16:11.451 drvModbusAsyn::doModbusIO port
XPP_Xn_Bit error calling writeRead, error=plc-xpp-vac02:502 timeout:
Resource temporarily unavailable, nwrite=6/6, nread=0


Any ideas?

Thanks

--
Alex Wallace
Control Systems Engineering
RED Controls & Data Systems
Bldg. 901 Room 130B
ext. 3516
cell (925)785-4338



References:
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