Hello gents, 

First of all, I'm not sure if this is possible or not, but I always assumed that it would be possible for two CPU's on the same network to be able to access any remote IO in the same network through Profinet IO. 

However, I'm not sure if this is possible or how to do it. Anyone ever done something similar? 

If I get your question well, you asked for a redundant system so despite the master PLCs type, the remote I/O should be only of ET200M type. -refereeing to SIEMENS standards - 

See the following link
http://w3.siemens.com/mcms/distributed-io/en/ip20-systems/et200m/pages/default.aspx

They will be two remote I/O placed in the same station ( using Profinet surely ), you will insert them in HW configuration and assign one of them to the first CPU and the other will assign to the other CPU.

please note:
If the master CPUs of S7-400 H system you will get a perfect hardware redundancy, if not, then you will need to do some programming in the background in order to reach an accurate software redundancy.

Regards;

Ahmed Kadry

Hello,

I'm not talking about a redundant system.

Imagine two S7-300 PLC's and a profinet remote IO block connected to one switch.

I assumed that both the PLC's could read the IO from the remote IO block since it's on the network, thus being truly distributed as signals that are useful for both PLC's can be read as needed by each PLC. 

But looking into the hardware configuration (when having two CPU's in the same project) this is not possible to do, so I assume it's not feasible at all.

Has anyone tried this or know if it's possible? Reading on Siemens website, it seems like this is only possible with Safety Cards and CPU's as a way of taking over equipment in case of equipment failure (which is interesting, but not what I want).

Hello bubulindo;

The best solution for your issue, Just assign the remote I/O to one of the CPUs and make a data transfer between the two CPUs using GET and PUT functions so surely you can get all I/O s in both PLCs at the same time.

If your problem solved, Just let me now.

Regards;

Ahmed Kadry

bubulindo

Hello,

I'm not talking about a redundant system.

Imagine two S7-300 PLC's and a profinet remote IO block connected to one switch.

I assumed that both the PLC's could read the IO from the remote IO block since it's on the network, thus being truly distributed as signals that are useful for both PLC's can be read as needed by each PLC. 

But looking into the hardware configuration (when having two CPU's in the same project) this is not possible to do, so I assume it's not feasible at all.

Has anyone tried this or know if it's possible? Reading on Siemens website, it seems like this is only possible with Safety Cards and CPU's as a way of taking over equipment in case of equipment failure (which is interesting, but not what I want).

 Hello,

 Two CPU Master or one Master and one Slave?

 Please specify your CPU type and how you want to connect your system

 https://cache.industry.siemens.com/dl/files/908/78028908/att_32073/v1/78028908_SIMATIC_Comm_DOKU_v21_e.pdf

 https://support.industry.siemens.com/cs/document/24352751/which-types-of-connection-protocols-do-the-s7-300-400-cpus-and-the-cps-support-by-default-?dti=0&lc=en-WW

Hi,

I agree with Ahmed , because two CPUs cannot read and write on a single io at a same time,u need to move with PLC to PLC communication to exchange data.

Hello, 

I'm using PCS7 and will use a profinet network with two S7-400 PLC's. 

The reason why I want to have both PLC's reading from the same remote IO is that I'm planning on leaving one remote IO in one of the cabinets and have some signals from the other cabinet (power supply status, OLM and OSM status, etc...) mapped into that remote IO (thus saving me the need to buy another Profinet node (yes, it looks weird, but my company is way too cheap). 

I had a look and it seems like this is possible with F-CPU's and cards, but that's way out of what I need. Also considering that timing is not an issue with these signals, I assumed it would be possible to have both CPU's reading from the same IO (allowing a bit of increase in redundancy). 

How would one go about to set up shared devices? 

Edit: The profinet manual specifies this. It's not exactly what I wanted as both CPU's cannot read the same signal at the same time and can only work on the sub-module level, but it's better than nothing. 

New question published by mamy is split to a separate thread with the subject How to communicate between cpu319 3pn dp & et200m via profinet?.

Best regards
Jen_Moderator