What Is a Protocol Converter?

Referred to as co-transformation, also called interface converter, it enables hosts on communication networks that use different high-level protocols to still cooperate with each other to complete various distributed applications. It works at the transport layer or higher. The interface protocol converter can generally be completed with an ASIC chip, with low cost and small size. It can convert the Ethernet or V.35 data interface of the IEEE802.3 protocol and the 2M interface of the standard G.703 protocol to each other. Can also be converted in 232/485/422 serial port and E1, CAN interface and 2M interface. ^[1]

Protocol converter

Referred to as co-transformation, also called interface converter, it can enable hosts on communication networks that use different high-level protocols to still cooperate with each other to complete various

The rapid development of computer network technology has created a large number of diverse network systems, leading to the problem of how to interconnect the various networks. One way is to implement international standards. International standards for 051 network architecture and communication protocols have become more and more mature. However, it is necessary to transform a large number of existing non-051 systems into 051 bodies.

Protocol conversion is a kind of mapping, which is to map the sending and receiving information (or event) sequence of one protocol to the sending and receiving information sequence of another protocol. The information that needs to be mapped is important information, so protocol conversion can be considered as a mapping between important information of two protocols. The so-called important information and non-important information are relative. They need to be determined according to specific needs. Different important information is selected for mapping, and different converters will be obtained. ^[3]

Industrial communication requires information sharing and data exchange between multiple devices, and the commonly used industrial control equipment communication ports include RS-232, RS-485, CAN, and networks. Due to the different interface protocols, operations and communication between heterogeneous networks Information exchange is difficult. Different interface devices can be networked through multi-protocol converters to achieve interoperability between devices. Based on a variety of communication ports and various protocols, a wide variety of protocol converters are formed. The main categories are E1 / Ethernet protocol converter, RS-232 / 485/422 / CAN converter / RS-232 / 485 / CAN converter and so on. . ^[4]

E1 / Ethernet Protocol Converter

E1 protocol converter 3one (2 photos)

The existing protocol converters based on E1 and Ethernet are mainly divided into E1 / Ethernet series and E1 / V.35 series. The use of E1 links to transmit Ethernet data has a wide range of applications in reality. Because E1 and Ethernet have different data transmission protocol standards, a protocol converter is required between them to complete the data conversion. Existing E1 / Ethernet protocol converters are based on the entire E1 transmission capability when converting data. ^[2]

It converts Ethernet signals or V.35 signals into E1 signals and transmits them over long distances on synchronous / quasi-synchronous digital networks in the form of E1 signals. The main purpose is to extend the transmission distance of Ethernet signals and V.35 signals. It is a network access device. ^[2]

Protocol gateways usually perform protocol conversion between network areas that use different protocols. This conversion process can take place between layers 2, 3, or 2 and 3 of the OSI reference model. However, there are two types of protocol gateways that do not provide conversion functions: security gateways and pipes. Due to the logical differences between the two interconnected network areas, the security gateway is a necessary intermediary between two technically similar network areas. Such as private WAN and public Internet. ^[2]

RS-232 / 485 / CAN converter

Based on the combination of centralized serial ports and different protocols, there are mainly RS-232 serial to 2M converters, RS-485 / 422 serial to 2MG.703 converters, RS-232 to 2ME1 converters, CAN to 232, 485 converters, USB TO RS-232 / 485/422 converter. ^[1]

RS232 / 485 / CAN interface converter (3 photos)

Devices with serial communication capabilities are still widely used in the field of control and communication. With the increase of access devices, the complexity of application functions has increased, and the disadvantages of traditional serial communication networks have become increasingly apparent. CAN intelligent converter, upgrade, transform or rebuild the existing communication or control network, can easily achieve RS232 equipment multi-point networking, remote communication, especially without changing the original RS232 communication software, users can Embedded directly into the original application field, making the system design reach a more advanced level, and in the case of greatly improved system functions and performance, reducing waste caused by repeated investment and system replacement. ^[1]

The primary function of the USB-RS232 interface converter is to implement the protocol conversion of the two buses. The host can use the new USB bus protocol to send data to the outside. The converter internally converts the data format into an RS232 serial signal and sends it to the device. The data returned by the device from the host is converted into USB protocol data by the converter. ^[5]

The USB-RS232 interface converter can add special functions when performing protocol conversion on the data flowing through. 1. Since the speed of the USB bus is much faster than the RS232 interface, a data buffer can be designed on the interface converter to coordinate the speed difference between the two buses. 2. There are some variants of the RS232 interface, such as RS485 and RS422 interfaces. RS232-RS485 or RS232-RS422 interface converters can be designed in the interface converter to simplify the communication interface conversion of the entire system. 3. When the interface converter performs data format conversion, encryption and decryption algorithms can be designed to process the data flowing through it, thereby improving the data confidentiality of the system. ^[5]

Fieldbus-based protocol converter

Based on the study of fieldbus, it was found that the competition and coexistence of multiple bus standards objectively caused inconvenience in application. ^[6]

The combination of the CAN bus protocol and the Modbus protocol, by referencing the Modbus protocol instead of the original custom serial port protocol, classifies communication tasks according to reading and writing, and then uses standard function codes defined by the Modbus protocol to simplify the communication process and improve efficiency, while also making use of The system is open and can easily form a network. The Modbus protocol is a master-slave protocol, and the CAN bus protocol is a multi-master peer-to-peer protocol. This also determines that the designed protocol converter acts as a slave in the Modbus network and as the node with the highest sending priority in the CAN network. ^[6]

Modbus and CAN protocol conversion principle: divide the storage buffers of Modbus messages and CAN messages (including the respective input and output buffers) in the RAM of the DSP; the messages received by the protocol converter from the Modbus master are stored in Modbus Receive buffer, read the data from the CAN bus receive buffer and send it to the Modbus response message format when the response is returned to the master station. The protocol converter obtains the message from the Modbus receive buffer and stores it in the CAN message transmission buffer. Area, based on the function code for sending analysis, decide whether to use single or split sending. In general, it is a store-and-forward mechanism. This mechanism first considers the reliability of communication conversion. The delay caused by storage conversion directly reduces the real-time communication. ^[6]