Skip to Content

SiePortal

The integrated platform for your product selection, buying and support workflow - bringing together Industry Mall and Online Support.

SiePortalDeutsch

Search

Home
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menu temporary not available
- Menue temporary not available
- {{item.title}}

Products & Services
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
MySiePortal MySiePortal
{{(apiData.MySiePortal | filter:{'rank':1}:true)[0].title}} MySiePortal
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Cart ({{apiData.CartCount}})

Navigation

WINCC Modbus TCP Function Code Problem

Created by: Priest at: 6/25/2012 6:46 AM (7 Replies)

Rating (1)

Thanks 0

8 Entries

6/25/2012 6:46 AM	Rate (0)
Priest Posts: 12 Rating: (0)	Dear All, I have a device which works as a gateway between SNMP devices and Modbus TCP. It is called Infrastruxure (struxureware) Central Server made by "APC by Schneider Electric" which collects data from SNMP devices on its 1st network port and maps the collected data into Modbus TCP register addresses and outputs on its 2nd network port. In its configuration I can map a slave address (Modbus TCP) to my SNMP devices and then map register addresses between 31000 to 39999 to any property on my devices. So on the Modbus TCP end I have the IP address of the Server and Slave address of my SNMP device and register number of my properties. This device works as a Modbus TCP Server and I should use 3xInput Registers. I tested the function using a software named "Modbus Poll" and it worked fine. I added modbus tcp tags to my WINCC project (WinCC 7 SP2) and used the IP of the server and the slave address of my device, selected the input registers and entered the register number. Unfortunately the wincc did not receive any data. I checked the server log and it constatnly repeats the message: WARN - Unsupported function: 3 It seems that the wincc is sending function code 3 no matter what area I chose in my tags. I am really stuck on this and any solution to this problem is much appreciated. Thanks
Priest Posts: 12 Rating: (0)
Suggestion To thank Quote Answer

6/25/2012 7:51 AM	Rate (0)
SteBo Platinum Member Joined: 10/3/2010 Last visit: 9/15/2025 Posts: 1568 Rating: (196)	Function code 3 is for reading holding registers 4xxxx Function code 4 is for reading input register 3xxxx Can you post a few screenshots of your WinCC configuration of tags?
	B r g d s , S t e B o SIMATIC HMI in Online Support Forum
Suggestion To thank Quote Answer

6/25/2012 8:32 AM	Rate (0)
Priest Posts: 12 Rating: (0)	As I said I need to poll the server using Function Code 4 (Read Input Registers). I attached some screens. Hope it helps Attachment Tag_screens.zip (394 Downloads)
Priest Posts: 12 Rating: (0)
Suggestion To thank Quote Answer

6/25/2012 8:50 AM	Rate (0)
Priest Posts: 12 Rating: (0)	One other thing. I used WireShark to monitor the network traffic and I found out a number of interesting behaviors. 1. Even if I delete all my tags, WinCC is sending a stream of packets with FC3 and address 0 repeatedly. 2. I tried changing the properties of my tag, selecting different areas but the packets continue to be just FC3 with address 0. 3. When I change the CPU type in the connection properties to Premium/Micro, packet changes to FC3, address 6785. Attachment Modbus_traf.jpg (424 Downloads)
Priest Posts: 12 Rating: (0)
Suggestion To thank Quote Answer

6/25/2012 12:32 PM	Rate (0)
SteBo Platinum Member Joined: 10/3/2010 Last visit: 9/15/2025 Posts: 1568 Rating: (196)	Priest One other thing. I used WireShark to monitor the network traffic and I found out a number of interesting behaviors. 1. Even if I delete all my tags, WinCC is sending a stream of packets with FC3 and address 0 repeatedly. 2. I tried changing the properties of my tag, selecting different areas but the packets continue to be just FC3 with address 0. 3. When I change the CPU type in the connection properties to Premium/Micro, packet changes to FC3, address 6785. I think it's better to start a Support Request for this one. Brgds.
	B r g d s , S t e B o SIMATIC HMI in Online Support Forum
Suggestion To thank Quote Answer

7/5/2012 1:06 PM	Rate (1)
nmnogueira Bronze Member Joined: 3/15/2010 Last visit: 7/30/2025 Posts: 137 Rating: (10)	Priest One other thing. I used WireShark to monitor the network traffic and I found out a number of interesting behaviors. 1. Even if I delete all my tags, WinCC is sending a stream of packets with FC3 and address 0 repeatedly. 2. I tried changing the properties of my tag, selecting different areas but the packets continue to be just FC3 with address 0. 3. When I change the CPU type in the connection properties to Premium/Micro, packet changes to FC3, address 6785. I found out the exact same thing. Apparently WinCC is continuously sending a "Read Multiple Registers" request to address 0 in order to see if the slave is responding. If there is no response from the slave, the connection is marked as down. If a response is received, the other registers (defined in the tags) are requested. This can lead to a couple of problems. One of them is that if the slave does not support the "Illegal address" or "Illegal function" exception code response, WinCC won't communicate with it at all. This is what I understood from some communication problems I've been having in the last months.

Suggestion To thank Quote Answer

8/10/2012 8:24 PM	Rate (0)
bantonio Posts: 18 Rating: (0)	I have the same problems and I saw the same things, Wincc asking for a register that doesn't exist in the slave and then problems in communications. I bypassed this problem increasing the update time of tags to 5 seconds, I'm reading 5 multimeters. At the beginning of communication Wincc ask for that register but after some seconds it starts to communicate without asking that register unavailable on device. Did you find a better solution?
bantonio Posts: 18 Rating: (0)
Suggestion To thank Quote Answer

8/10/2012 9:19 PM	Rate (0)
Priest Posts: 12 Rating: (0)	Dear Bantonio, Your solution is very clever. I could not find any solution and I used a Modbus TCP opc server to solve the issue. I will check your solution whenever I find the time. Thanks
Priest Posts: 12 Rating: (0)
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Related topics by keywords:

WinCC Communication (OPC, S7, OtherSystem)

Follow us on