MESSAGING APPLICATION LAYER (MODBUS) OVER ETHERNET TO TRANSPORT LAYER (TCP) COMMUNICATIONS METHOD AND APPARATUS

摘要

A communications adapter is provided for interfacing between a master device and an I/O device (body) having an output and/or an input. In the case of the I/ O body having an output, the adapter has a TCP port for coupling to the master device via a transmission path for receiving a request message. The adapter also has a connector for operable coupling to the I/O device for receiving the output of the I/O device. The adapter further has an interface circuit operably connected to the TCP port and the connecto r for transmitting a response message over the transmission path in response to th e request message, the response message correlating to the output received from the I/ O device. The request message and the response message is limited to a length that is less than a TCP transaction length and/or a maximum transmission unit limit, or both, depending on the embodiment of the present invention.