from the Forum department...
modbus communication
Communications systems and equipment. topic
Posted by shammy on 5 August, 2013 - 11:09 am
We tried to establish modbus communication between Yokogawa DCS CS3000 and Honeywell PLC Safety Manager through RS485 serial link. But DCS displays a message saying error code A3C6 and it recovers after few seconds. Again the error appears and recovers. Thus this cycle repeats continuously. The description of the error code is "response message error, Received data length error". We rechecked all the parameters set for communication at both PLC and DCS end and ensured same values are set. But we could not find a way to solve the problem. Suggestions of the members are highly appreciated.

Posted by Harvard on 5 August, 2013 - 1:39 pm
RS485 is a Half Duplex communications physical layer. In other words each device (MASTER or SLAVE) must KEY UP, delay, SEND TX, delay and KEY DOWN. So if the Slave RESPONSE does not wait until the Master has KEYED DOWN you would have this kind of experience.

Posted by shammy on 6 August, 2013 - 12:55 am
Using the modscan software we could see the value of each bit on a laptop. But the problem occurs when connected to the DCS

Posted by Jerry Miille on 5 August, 2013 - 5:00 pm
If you can capture the hex bytes on the communication wires and send the messages to me, I will analyze them to see what is happening. A great tool that I use to capture and time-tag messages is the Versa-Tap from Stratus Engineering.

Jerry Miille (jmiille [at] miille [dot] com)

Your use of this site is subject to the terms and conditions set forth under Legal Notices and the Privacy Policy. Please read those terms and conditions carefully. Subject to the rights expressly reserved to others under Legal Notices, the content of this site and the compilation thereof is © 1999-2014 Nerds in Control, LLC. All rights reserved.

Users of this site are benefiting from open source technologies, including PHP, MySQL and Apache. Be happy.

If money can't buy happiness, I guess you'll just have to rent it.
Advertise here
Servo, stepping motor control, analog & web HMI in one system!
Time to incorporate data handling, web HMI and motion in one system!
Servo, steppers, analog, digital & web HMI - Fully Integrated! is the largest Automation community on the web. Learn how to advertise here now...
View free setup and multi-vendor EtherCAT demo videos online
our advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive