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netRAPID for Real-Time Ethernet in two characteristics
In course of decentralization in automation technology control functions and increased IT functionality is shifted into the high-performance processors of field devices. Furthermore these intelligent field devices shall be connected to the “Internet of things” to provide analytical-, condition- or diagnostic data to a cloud application.
Besides performant Real-Time Ethernet the basic prerequisite is access to standard Ethernet services over a shared cabling. Ideally, the central communication unit already contains basic IT functions, for example a webserver, as well as fundamental IoT functionality, such as an integrated OPC UA Server or MQTT client.
The use case: With integrated OPC UA / MQTT, field devices can provide "value added data" to an edge device or directly to a cloud using the same physical cable.
|With its integrated Ethernet transformer and sole usage of the netX internal RAM, netRAPID 52-RE is optimized for minimum footprint. Its focus is purely on Real-Time Ethernet communication for compact field devices.|
With an additional SDRAM instead of the Ethernet transformers, the netRAPID 51-RE is optimized for advanced features. Besides Real-Time Ethernet communication there is an integrated WebServer as well as an additional transparent Ethernet channel available, to realize own IT solutions in the host processor of the automation device. Moreover, in mid-2018 an upgrade with integrated OPC UA server and a MQTT client is available.
Common Software structure to the application
As common interface for the data exchange to the host processor netX based products use an internal Dual-Port-Memory. It has a clearly defined layout, consisting of a system channel, a handshake channel and up to 4 communication channel, which can be used for independent functionality / protocols.
The numbers of communication channel offered to the application varies, depending on the functional range of the used netX firmware. Common to all solutions is that the Real-Time Ethernet data is always mapped into the first channel (Channel 0).
In maximum configuration, netRAPID 51 offers three separate channels, which can be accessed by the host processor using a 50MHz SPI interface:
Cyclic and acyclic Real-Time Ethernet data
Ethernet channel with TCP socket or Raw Ethernet interface
IoT data via OPC UA / MQTT (available from mid-2018)
Host Connection via fast SPI
Depending on the product, access to the netX internal Dual-Port-Memory will be done either with 8/16bit parallel bus (DPM mode) or serial by 50MHz SPI interface (SPM mode).
In DPM mode, typically only Channel 0 for Real-Time Ethernet can be accessed (address lines: A0 – A13). Whereas in SPM mode the application can always access Channel 0 for Real-Time Ethernet as well as Channel 1 and 2 for additional IT & IoT functionalities.
The following table shows the mapping of the Ethernet protocols to the communication channels of the respective host interface mode:
|Host interface mode||Channel 0: |
|Channel 1: |
|Channel 2: |
IoT data (planned)
|DPM mode||I/O data||-||-|
|SPM Mode||I/O data||TCP/UDP||Data via MQTT|
|acyclic communication||Raw Ethernet||Data via OPC UA|
As for all netX-based products, netRAPID 51 owns 4 MAC addresses (MAC0 – MAC3). Per default these are taken from the Hilscher MAC Address pool and will be added during manufacturing. MAC0 to MAC2 are reserved for the Real-Time Ethernet communication and MAC3 is allocated for separate Raw Ethernet communication. The split of the incoming Ethernet traffic to the separate MAC addresses already takes place in the Real-Time Ethernet switch of the netX controller.
To implement Internet protocols or Ethernet services, the application uses Channel 1 of netRAPID 51. Depending on the requirements of the application, either TCP socket mode or Raw Ethernet mode can be used.
In TCP socket mode the host application can connect own UDP/TCP based services via the offered socket interface to the network. Here the netX integrated TCP/IP stack and IP address will be utilized. The host application will be present in the network with the same network parameters as the Real-Time Ethernet protocol.
In Raw Ethernet mode the host application can transparently access the network, as if it had a separate network adapter. The connection will be realized in the netX Real-Time Ethernet Switch using a separate Ethernet MAC address. Doing so the host application can be seen as individual device in the network and can freely select its own network parameters. (e.g. the IP address of a Linux host system integrated TCP/IP stack)
netRAPID NRP 51-RE has 4 MAC addresses: MAC0 to MAC3.
|MAC address||Protocol||Communication Channel|
|MAC0||Real-Time Ethernet protocol||Channel 0|
|TCP, UDP||Channel 1|
|MQTT, OPC UA||Channel 2|
|MAC1 and MAC2||Used by Real-Time Ethernet protocol.||Channel 0|
|MAC3||Raw Ethernet||Channel 1|