RuggedCom RX1000, RX1100 manual Serial Protocols Applications, Character Encapsulation, RTU Polling

RuggedRouter™ User Guide

Serial Protocols Applications

Character Encapsulation

Character encapsulation is used any time a stream of characters must be reliably transported across a network.

The character streams can be created by any serial device. The baud rates supported at either server need not be the same. If configured, the router will obey XON/XOFF flow control from the end devices.

One of the routers is configured to listen to TCP connection requests on a specific TCP port number. The other server is configured to connect to its peer on the listening port number. The RuggedRouter will attempt to connect periodically if the first attempt fails and after a connection is broken.

The RuggedRouter can be used to connect to any device supporting TCP (e.g. a host computer’s TCP stack or a serial application on a host using port redirection software).

RTU Polling

The following applies to a variety of RTU protocols besides ModBus RTU, including ModBus ASCII and DNP.

The remote router communicates with host equipment through:

∙native TCP connections,

∙another RuggedRouter's via a serial port or

∙a port redirection package which Supports TCP.

If a RuggedRouter is used at the host end, it will wait for a request from the host, encapsulate it in a TCP message and send it to the remote side. There, the remote RuggedRouter will forward the original request to the RTU. When the RTU replies the RuggedRouter will forward the encapsulated reply back to the host end.

ModBus does not employ flow-control so XON/XOFF should not be configured.

The RuggedRouter maintains configurable timers to help decide replies and requests are complete and to handle special messages such as broadcasts.

The RuggedRouter will also handle the process of line-turnaround when used with RS485.

Broadcast RTU Polling

Broadcast polling allows a single host connected RuggedRouter to “fan-out” a polling stream to a number of remote RTUs.

The host equipment connects via a serial port to a RuggedRouter. Up to 32 remote RuggedRouters may connect to the host server via the network.

Initially, the remote servers will place connections to the host server. The host server in turn is configured to accept the required number of incoming connections.

186 RuggedCom