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I/O modules • 257

Data exchange modules 750-654

4.8.1.1.4 Data exchange module 750-654

Technical description

This technical description is only valid for hardware and software version X X X X 2 C 0 0 - - - -. The product series number is printed on the right side of the module.

The data exchange module allows the exchange of data between different fieldbus systems.

Two modules are a communication pair that is connected by means of two twisted wire pairs. Each module is part of a fieldbus node.

The data exchange is done in full duplex operation, independent of the fieldbus system used. The data of the output process image of the fieldbus coupler is transmitted to the communication partner. This module then transmits the data to the input process image of its fieldbus coupler and vice versa.

Factory preset transmission is 32 bits of input data and 32 bits of output data. Data transfer time for 32 bits of I/O is about 5 ms.

The LED “Function“ indicates a data exchange with the buscoupler. The status of the data transmission is indicated by the TxD and RxD LEDs.

The data exchange module can operate with all WAGO-I/O-SYSTEM buscouplers (except for the economy type).

Modular I/O System

ETHERNET TCP/IP

258 • I/O modules

Data exchange modules 750-654

Description of data exchange module:

The data exchange module allows for the exchange of 4 (5) bytes between different fieldbus systems via multiplexing of a serial connection. The delay which is caused by the multiplexor is < 5ms. The integrated watchdog function switches all outputs to zero if there is no valid information for more than 200 ms via the multiplex connection.

The 128 bytes input buffer provides for high rates of data transmission. When using slower speeds, you can collect the received data with lower priority without loosing data.

The 16 byte output buffer provides for faster transmission of larger data strings.

The data exchange module is connected peer-to-peer. For the wiring of the serial multiplex connection the RxD and TxD cables are crossed. The following illustrations show the peer-to-peer connection and the internal structure of the data exchange module.

Modular I/O System

ETHERNET TCP/IP

I/O modules • 259 Data exchange modules 750-654

Point to point connection

Output byte 0

7 6 5 4 3 2 1 0

Output byte 1

7 6 5 4 3 2 1 0

Output byte 2

7 6 5 4 3 2 1 0

Output byte 3

7 6 5 4 3 2 1 0

Organization of the input and output data:

The module is a combination of a special function input and output module with 1 x 32 (40) Bit input and output data. The transfer of the data to be transmitted and the received data is made via 5 input and 5 output Bytes. One control byte and one status byte are used to control the floating data.

Modular I/O System

ETHERNET TCP/IP

260 • I/O modules

Data exchange modules 750-654

The control byte consists of the following bits:

The status byte consists of the following bits:

The PLC is able to control transmission and reception of data by means of the control byte and the status byte.

Control of the multiplex connection:

In the process image of the transmitting buscoupler, one Bit is set to "1" for the whole time. As long as this Bit is "1" in the receiving coupler, further input Bits can be evaluated. If the Bit is "0" the multiplex connection has been disrupted. The further Bits are also 0 because of the watchdog.

Control of the multiplex connection with acknowledge:

If the transmitting buscoupler gets an acknowledge from the receiving buscoupler, the received bit must be transfered as an output bit to the process image. The transmission is successful as long as the Bit is "1".

Handshake:

If a serial data exchange should be made with the data exchange module, the handshake can be made via "Toggle Bits". Therefore an input bit and an output bit are reserved. As soon as those bits are different from each other, a request from the opposite module is made. As soon as the request is executed the output bit is toggled

Modular I/O System

ETHERNET TCP/IP

ETHERNET • 261

5 ETHERNET

ETHERNET is a technology, which has been proven and established as an effective means of data transmission in the field of information technology and office communication. Within a short time ETHERNET has also made a successful breakthrough in the area of private PC networks throughout the world.

This technology was developed in 1972 by Dr. Robert M. Metcalfe, David R. Boggs, Charles Thacker, Butler W. Lampson, and Xerox (Stanford, Ct.). Standardization (IEEE 802.3) took place in 1983.

ETHERNET predominantly uses coaxial cables or twisted pair cables as a transmission medium. Connection to ethernet, often already existing in networks, (LAN, Internet) is easy and the data exchange at a transmission rate of 10 Mbit/s is very fast.

ETHERNET has been equipped with higher level communication software in addition to standard IEEE 802.3, i.e. TCP/IP (Transmission Control Protocol / Internet Protocol) to allow communication between different systems. The TCP/IP protocol stack offers a high degree of reliability for the transmission of information.

In the ETHERNET TCP/IP fieldbus coupler developed by WAGO, the following application protocols have been implemented on the basis of the TCP/IP stack:

•a MODBUS/TCP server,

•a BootP client and

•an HTTP server.

These protocols allow the user to create applications (master applications) with standardized interfaces and transmit process data via an ETHERNET interface.

Information such as the fieldbus node architecture, network statistics and diagnostic information is stored in the fieldbus coupler and can be viewed as HTML pages via a web browser being served from the HTTP server in the buscoupler (Microsoft Internet-Explorer, Netscape Navigator,...). Through the WAGO IO Pro 32 software it is possible to create your own webpages and store them in the coupler for control of the PFC program (this is for the 750842 PFC only.)

The WAGO ETHERNET TCP/IP fieldbus coupler does not require any additional master components other than a PC with a network card. The fieldbus coupler can be easily connected to local or global networks using the RJ45 connector. Other networking components such as hubs, switches or repeaters can also be used. However, to establish the greatest amount of “determinism” a switch is recommended.

The use of ETHERNET as a fieldbus allows continuous data transmission between the plant floor and the office. Connection of the ETHERNET TCP/IP fieldbus coupler to the Internet even enables industrial processing data for all

Modular I/O System

ETHERNET TCP/IP