RuggedCom RS400 manual Broadcast RTU Polling

Serial Protocols

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

RuggedServer™ maintains configurable timers to help decide if replies and requests are complete.

RuggedServer™ will also handle the process of line-turnaround when used with RS485. It is important to mention that unsolicited messages from RTUs in half-duplex mode can not be supported reliably. Message processing time includes sending a message over RS485, a packtimer and a turnaround time. In order to handle half-duplex mode reliably, the turnaround time must be configured long enough to allow an expected response to be received. Any other messages will not be sent to the RS485 line within the processing time. If such a message is received from the network, it will be delayed. It is up to the application to handle polling times on ports properly.

2.2.1.3 Broadcast RTU Polling

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

The host equipment connects via a serial port to a RuggedServer™. Up to 64 remote RuggedServers™ may connect to the host server via the network.

Figure 32: Broadcast RTU Polling

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

The host will sequentially poll each RTU. Each poll received by the host server is forwarded (i.e. broadcast) to all of the remote servers. All RTUs will receive the request and the appropriate RTU will issue a reply. The reply is returned to the host server, where it is forwarded to the host.

ROS™ v3.5 56 RS400