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

Question about CP341

Created by: Jazz_M at: 6/24/2010 3:34 PM (12 Replies)

Rating (2)

Thanks 1

Result pages:: |; 1 | 2; |

13 Entries

Entries per page: 10 | all

6/24/2010 3:34 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	hi darius I have a same system like solution riders Well i have used Cpu 315-2dp in R connection i have a CP341 in slave configuration. Well my question how can i program the or should i say when the data transfer to CP341 should not be affected by cpu changeover. I have attached the hardware configuration, Splitted from CP431 Redundancy.
	Last edited by: O_Moderator at: 6/25/2010 11:53 AM new subject after splitting Jazz
Suggestion To thank Quote Answer

6/24/2010 3:46 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	hi darius I have a same system like solution riders Well i have used Cpu 315-2dp in R connection i have a 2 x CP341 in slave configuration. Well my question how can i program the or should i say when the data transfer to 2 x CP341 should not be affected by cpu changeover.Rnf:lblSmileyTooltip_
	Last edited by: Tagolover at: 6/24/2010 4:21 PM attachment not included Jazz
Suggestion To thank Quote Answer

6/24/2010 3:59 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 3/15/2025 Posts: 2957 Rating: (243)	Hello, I have no big experience in that kind of systems, but anyway don't understand your question. You have only one CP341 module, so I don't see problems here. I have talked about problem when you need redundant modbus, but not modbus on redundant system. I talked about problem if you have two CP341, because modbus is not initially designed for redundancy.
	Best regards, Darius
Suggestion To thank Quote Answer

6/24/2010 4:22 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi Darius sorry for that mistake, I have 2 cp 341
	Jazz
Suggestion To thank Quote Answer

6/24/2010 6:09 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 3/15/2025 Posts: 2957 Rating: (243)	... and they are slaves and must redundant ? Ok if they are slaves then situation is better. Master sends message to slave and both CP341 will get the message. Software must be written so like only one CP341 will reply to request. In that case master will think that it talks to normal slave (no redundancy). But in what case you will switch CP341 ? Other question is how you will make cabling ? Master outputs only one line RS485 and you need two lines for redundancy. How you implement this ? If you intend to connect redundant slaves in sequence then why do you need redundancy at all ?
	Best regards, Darius
Suggestion To thank Quote Answer

6/25/2010 7:10 AM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi Darius Well correct me if i am wrong, All this redudancy is only to have data consistency right. Say if i conviece my customer to have two masters at his end will it solve my case. Or should i say can i have a switch that is external that will switch between two cp341 and give a single o/p Again i am trying out options here...
	Jazz
Suggestion To thank Quote Answer

6/25/2010 3:24 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 3/15/2025 Posts: 2957 Rating: (243)	Communication processor redundancy is for physical line problems I think. If there is a problem in physical line or in one of the communication processors then you work with another and in this time you can repair first. In case of modbus there is bigger problem. It is not originally designed for redundancy, so implementation of it is a little bit complicated. If you will have two masters talking to two slaves then it will not solve your problem. It will be just two independant systems. In that case if one system fails second will be working and getting the same data. It will be some kind of pseudo redundancy. Anyway if you need real redundancy you should go to Profibus or Profinet or at least Modbus TCP protocol. There are some solutions to make it redundant.
	Best regards, Darius
Suggestion To thank Quote Answer

6/26/2010 12:47 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Darius is correct. It is very difficult to make a true redudant modbus system, where both CP have the same slave address. In my experience, what you usually end up with is 2 independant modbus slaves with different slave adresses and the master polls both for data, so if slave system were to fail, they could still get data from the working one. The master could have 2 communications ports, or have some software that automatically starts polling the backup slave address if the main one fails. The way the master polls the slaves in these systems can very a lot. I have come across:- 1) The master randomly polls one or the other. 2) The master polls both slaves alternatively. 3) The master only polls one slave until it fails and it then switches over to the other. If both fail, the master will "hunt" between the to slaves and then settle on the first one that starts working again. In this case, I have also seen systems where the master periodically tests the backup slave by sending a test poll occaisonally, so that the redundancy can be assured. 4) The master polls one slave for a fixed time (e.g. 1 hour), then polls the other for a fixed time. In theory it could be possible to make a system with both slave having the same slave address, but it would need some form of external switching using a relay. I have engineered a system like this once and it seemed to work ok Assuming RS485. What you would need is a DPDT relay. The masters + and - connections would be connected to the poles and one CP341 (rack 0) connected to one throw and the other CP341 (rack 1) connected to the other throw. You would then need to write some logic in the PLC that detected which CPU is the master and which rack it is in. You would need to use the RDSYSST SFC to read the H-System parameters. I have done this already if you want some example code. So the logic would be:- IF CPU is master and this is Rack 0 switch relay to rack 0 position. IF CPU is master and this is Rack 1 switch relay to rack 1 position. So only the CPU that is the master will have data routed to its CP341. As both CPU's cannot be master at the same time, there is no danger of the relay being continually switched between both positions. The attcched picture shows my thinking. It is shon in the rack 0 is the master CPU state. Attachment dual redundant cp341.jpg (169 Downloads)
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
Suggestion To thank Quote Answer

6/26/2010 1:38 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi Smiffy Thankyou and darius for the reply, Well i too was thinking the same thing as the reduducany is not possible in CP341 modbus. My customer is still asking the same. I have hard time convincing him. I shall try once again. Let us hope for the best. Thank you all once again.
	Jazz
Suggestion To thank Quote Answer

6/26/2010 9:02 PM	Rate (2)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Tagolover Well i too was thinking the same thing as the reduducany is not possible in CP341 modbus. It is not impossible - just difficult. You could just offer him 2 independant slave devices. This could be:- i) 2 separate point-to-point networks. There is no reason with this method why the slave devices could have the same slave address. The master would need to have to separate serial interfaces. ii) 2 slaves on the same network. For this, the slaves would have to have different slave addresses. They could then both multi-dropped onto the same link to the master, which would only need one serial interface. Either way, the master would have to have some intelligence in such that it would poll one slave or the other in one of the ways I suggested in my earlier post. Or you could use the relay method and both slave could have the same slave address and be on the same interface to the master.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on