1, MPI is a Multi-Point Interface, suitable for PLC 200/300/400, operator Panel PC MPI/PROFIBUS and TP/OP communication card, supported MPI network communication speed for the network communication speed of 12Mbit/s. MPI network can connect up with 32 nodes, maximum communication distance is 50m, but can use repeaters to extend the length.
PPI Protocol is a communications protocol developed specifically for S7-200. S7-200 CPU communication port (Port0, Port1) support PPI Protocol, S7-200 some of the modules also support the PPI Protocol for communication. Micro/WIN programming through the PPI Protocol for communication with the CPU. PPI is a master/slave Protocol, the main station, from the station in a token ring network. A PPI network, with one station is standing and there is no limit to the number of, but one of the primary stations in the network number cannot be more than 32. Main station can both read and write data from the station, and also can read and write to master station data. In other words, S7-200 as the PPI at the main station, you can still respond to requests for data from other stations.
MPI is the communication between a master station; PPI can be more than one communication between the master and the slave.
2, the MPI protocol: Siemens internal agreements, the public;
PROFIBUS-DP Protocol: a standard protocol, open.
3, MODBUS MODICON company first advocated, a kind of communication protocol, after the majority of the company‘s application came to be recognized and become a standard communication protocol, as long as the communication or transmission of data in accordance with this Statute, different systems can communicate. At present, during the process of RS232/RS485 communications, even more widespread adoption of this Statute.
MODBUS communication protocol commonly used, there are two, one is the MODBUS ASCII, one is the MODBUS RTU.
In General, communications data volume and is mainly text communication using MODBUS ASCII protocol, large amount of data and communications data is a binary value, uses the MODBUS RTU Protocol.
In the course of practical application, in order to solve a particular problem, people like you can modify the MODBUS Protocol to meet their own needs (in fact, people often use their own definitions of the Statute to communication, this can solve the problem, but not specification). The more common usage is, little statutes, but the format of the Statute in the software manual, or directly in the help, which facilitated communication.
3. PPI,MPI and the PROFIBUS is based on the OSI (open System Interconnection) seven–layer network model, in line with European standard EN50170 PROFIBUS standards defined by, and token–based network communication protocols. These protocols are synchronous (serial) communication protocol based on characters and character format consists of a start bit, 8 data bits, parity bits, and one stop bit. Communication includes specific starting and ending character, source and destination address, frame size, and checksum data.
Baud rate, address different circumstances, PPI,MPI and PROFIBUS can run simultaneously on a network, and non–interference.
This means that if a network has S7-300, between S7-200,S7-300 by MPI or PROFIBUS communication, while at the same time on the same network TP170 if there were other main station in a communications network (TD 200, or the computer), and Micro/WIN programming, monitoring is required, this is the main network programming.
Using Siemens equipment can realize Micro/WIN of more of the following main station programming:
Micro touch screen to communicate with a S7-200 CPU.
Uses intelligent multi–master cable and Micro/WIN V3.2 SP4 or later. New cable can pass the token on the Web, which supports multiple host network programming.
If you use the CP cards, such as CP5511/CP5512 (laptop PCMCIA card), CP5611 (desktop PCI card), can support multiple master program communication.
If the CP card programming, select MPI protocol, note that MPI primary site cannot be accessed as PPI–master CPU.
If there are third party products connect to a main station on the network, users need to consult a third party product providers to see whether support Siemens S7-200 multi station network. Main station programming, programming computers to not only support other devices on the Internet there are many master station communication capabilities.
Earlier master station connection relies on computer hardware and Windows operating system. With the development of computer technology, has been unable to do much in most cases master program communications. Siemens main station programming users are advised to use cables or CP card communication combined with multi–master Micro/WIN programming.
4. MPI (Multipoint interface) is the SIMATIC S7 communication interface is a network for communication between apply to a few sites, used for connection between PC and a small number of close communication between the PLC.
Through PROFIBUS cables and connectors, S7-300 or S7-400 of the controller CPU with MPI Programming own PPI and S7-200CPU communication ports are connected, as well as with the programming port of the PC card (MPI/DP) via MPI or PROFIBUS cable connection can be realized. Can of course not included in the network PC and PLC only.
MPI communication rate for 19.2K~12Mbit/s, MPI of directly connecting with S7-200CPU communications network, the maximum rate is usually 187.5Kbit/s (S7-200CPU maximum speed limit).
In the MPI network can have up to 32 stations, one segment of the maximum communication distance is 50 meters (communication baud rate 187.5Kbit/s), long distance communication is available through the RS-485 Repeater extension.
MPI allows active–active communication and master–slave communication, each S7-200CPU communications connections for 4.
MPI protocol cannot have the same as PPI–master of S7-200CPU communications, S7-300 or S7-400 must ensure that communicating with the S7-200 the S7-200 CPU no further PPI–master, Micro/WIN cannot be accessed through the MPI protocol as PPI–master of S7-200CPU.
S7-200CPU only does MPI from the station, that is S7-200CPU cannot communicate through the MPI network, communicate only through the PPI. STEP 7-Micro/WIN and S7-200CPU MPI master–slave connection is established. Hardware use a CP5611 card plus MPI or PROFIBUS cable, S7-200 CPU communication port to be used on the programming port of the network connector. S note: CP5613 not available through MPI and programming S7-200 CPU communication port communications. 7-200CPU minimum rate of correspondence can be set to 19.2K, up to 187.5K.
S7-300 and S7-400 CPU as the main station XGET MPI (SFC67) and XPUT (SFC68) command reads the S7-200 data communications of up to 64 bytes of the packet. S7200 CPU does not need to write any program associated with the communication, only need the data to be exchanged into a continuous v store.
5. the S7-200 support the Modbus communication protocol in the following ways:
S7-200 on CPU communication port Port0 supports Modbus RTU Protocol become Modbus RTU slave. This functionality is achieved by S7-200 free port communication mode, so you can slow communication devices such as wireless data radio transmission.
If you want to S7-200 between CPU, or other support devices using the Modbus RTU Protocol Modbus RTU communications needed by S7-200 CPU Modbus master. S7-200 CPU decisions must be made by the users themselves in free mode, according to the relevant protocol programming.
To implement Modbus RTU communication, need to STEP 7-Micro/WIN32 programming software V3.2 or later and install STEP 7-Micro/WIN32 V3.2 Instruction Library (repertoire). Modbus RTU via the instructions prepared in advance in the library function blocks implementation of the program. Modbus RTU slave directive only supports communication 0 port on the CPU (Port0).
1. the Modbus RTU master instruction library function is called in the user program function block implementation of programmed procedures in advance, the library to Port 0 and Port 1 active. This directive sets a communication interface works in free mode.
2. the Modbus RTU Master directive used some user interrupt function and other programs cannot be disabling interrupts in user programs.
3. the Modbus RTU master version required for CPU. CPU versions must be 2.00 or 2.01 (order no 6ES721*-***23-0BA*), prior to version 1.22 (1.22 version) S7-200 not supported by the CPU.
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