Hi all.

Just a quick one. I am looking for an answer as to why you would use a DP-DP coupler to bridge 2 DP networks instead of using the Get/Put blocks?

Cheers

Hello,

my quick idea is that there are 2 PB DP networks independed and each has own Master. That networks need share some data and only PB DP is possible maybe due HW cfg. Take f.ex. 2x S7-300 (315-2 DP) only with PB DP ports on CPU. Yes, there are also maybe other possibilities but not S7 PUT/GET.

Update: hope it's clear from attachment, only example of my idea.

Duris_I

Hello,

my quick idea is that there are 2 PB DP networks independed and each has own Master. That networks need share some data and only PB DP is possible maybe due HW cfg. Take f.ex. 2x S7-300 (315-2 DP) only with PB DP ports on CPU. Yes, there are also maybe other possibilities but not S7 PUT/GET.

Update: hope it's clear from attachment, only example of my idea.

 Thank you.

Are you saying that some CPU's don't support the GET/PUT feature? And in those instances, if you wanted to share data between the PB DP networks, then the DP-DP coupler is the only option?

Hello,

no, I want maybe (better) to say that all S7 controllers support S7 (also included versions of this protocol) but not via all interfaces/HW, actual network requirements. You simply need find best option/solution due your existed HW or do other steps maybe with modification or buy new component/HW which add that capability. With DP Coupler is simply easy solution to 'join'together 2 independed PB networks where you need share some amount of data and you can't do/change  one of Masters to Slave on that other partner Master network, simply then you can share its data because it can be set as Slave but this maybe isn't possible as i said. There must be functional 2 independed PB networks and no changes are allowed. Sry, hope you understand my idea. maybe other one can better give other example, from my experience I have quick idea only...

What are the properties of DP DP coupler?

• Dual power supply
• Electrical isolation between the DP networks
• Different transmission rates and Profibus addresses on both sides of the coupler
• DP1 is supported with uniform and full diagnostic functioning
• It is robust. That means even if one side fails, it will retain the output values of the other side
• Offers up to 16 input/output areas for data transmission
• Of the 244 bytes of input and output data exchanged, 128 bytes are consistent
• Easy to set up the Profibus addresses using software or DIP switches
• Profibus-DP up to 12 Mbps
• Automatic baud rate recognition

For safety reasons, the DP DP coupler can be coupled with two different power sources concurrently.

The DP DP coupler allows the Profibus to rapidly transfer the processed data between the decentralized field modules like drives or slaves and central controller modules like PC or PLC.

During normal operation, the central controller cyclically reads the input of the connected decentralized field modules for sending the output data to them. The maximum of 244 bytes of output and input data can be transferred in one cycle.

Apart from the user data traffic, the DP DP coupler offers wide-ranging diagnosis and authorizing functions. The current diagnosis messages of the decentralized modules are summarized in the central controller modules. This enables a rapid localization of errors.

Hello.

There is one aspect that is not mentioned about DP/DP couplers. Security. 

With PUT/GET the program designer of the local PLC is trusted to only link to data of the remote PLC to which he/she is authorized to. There is however no security measure that prevents the local PLC designer to reach for other data and over-write it.

A DP/DP coupler is configured as if two independent devices. Each half is configured to be a slave in the Profibus network that it is configured into. Internally the data entering/exiting on one half is mapped to exit/ent on the other half. It is a fixed mapped configuration. Data flow beyond the limitations of the mapping is not possible.

The devices in one network is not exposed to data breaches of the other network. A fixed mapping dictate data flows through the DP/DP coupler.

Think of the DP/DP coupler as a man-in-the-middle playing the role of a firewall between two networks that do not trust each other.

Aside .. Electrically a coupler is a 'modern' ⁽¹⁾ version of using "potential free contact" relays used to interface between two systems to integrate them.

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