Think about it

Traditional TCPIP communication establishes a unique socket based on IP and Port, and completes the relevant communication through this socket, so what is the communication based on PROFINET?Let’s start by simply exploring and learning.

Operation Mode

• System engineering: In order to implement a system engineering, it is necessary to import the GSD file (general station description) of the device, which is provided by the device manufacturer. After importing, the modules defined in the GSD file need to be/submodules are configured to map it to the actual system and assign it to a slot/subslot; in addition, each slave device is assigned a logical name that should refer toThe function or installation location of the device in the system and used to assign IP addresses during address resolution, the total number of name assignments uses the DCP protocol (Discovery Configuration Protocol), which is integrated by default in every PROFINET device.
• Download system information to the controller: After the system engineering is completed, the system data needs to be downloaded to the controller, so that the controller has all the information needed to address the device and exchange data.
• Address resolution before system startup: Before interacting with a device, usually the controller must assign an IP address to the device before the system starts.System startup refers to the startup/restart of an automated system after a "power-up" or "reset".IP addresses within the same subnet are assigned using the DCP protocol integrated by default in each PROFINET field device, if the field device and the controller are in different subnets, address resolution is provided by a separate DHCP server (name->IP address).
• System startup: After the controller starts/restarts, it always starts the system according to the configuration data. During system startup, the controller establishes the application relationship (AR) and the communication relationship (CR)), configure and parameterize the process-level IO if necessary.
• Data exchange: After the system startup is successfully completed, the controller and the device exchange process data, alarms and aperiodic data.

DCP

The DCP protocol (Discovery Configuration Protocol, according to IEC 61158) is used as the basis for name/address resolution and is also part of the overall concept of "device replacement without programming devices", which can be used to read and write parameters required for device addressing,And write data to field devices, these services are real-time and only available in the subnet.

• Identify request->find a specific name
  Multicast service with a specific Frame_ID, sent to field devices to read device identification information, field device name assignment is mainly related to "DCPIdentify".req” is related to two functions: ① to ask which parameters are already included in the device in order to perform selective assignment of names; ② to search for a specific name to prevent duplicate addressing;Search, all devices without a name assigned must answer, if the call contains a specific name, only devices with that name will answer.

• Identify Response->Look for a specific name
  The "DCPIdentify.res" frame is a real-time frame with an Ethertype of 0x8892.In "DCPIdentify.res", the controller receives a reply indicating which options are satisfied by the device, this information is in the "DCPIdentify.Response" data field.

• Set Request->Write Name or IP Address to Device

• Set Response -> Confirmation of Set Request

Name Assignment

Since many devices of the same device type may be installed in the same system, it is necessary to assign a system-specific name (NameOfStation) to the field device, which must be written to the device by the engineering tool before the system starts.Since it will be used by the controller for name and address resolution before the system starts, the device name must be memorized in the field device.

Package capture process: External reference link: