User guide

RUGGEDCOM ROS
User Guide
Chapter 5
Setup and Configuration
Broadcast RTU Polling 115
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Figure 76: RTU Polling
1. Host 2. Host with Port Redirection Software 3. RMC30 4. Ethernet 5. RTU
If a server 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 server will forward the original request to the RTU. When the RTU
replies, the server will forward the encapsulated reply back to the host end.
The server maintains configurable timers to help decide if replies and requests are complete.
The server also handles the process of line-turnaround when used with RS485. It is important to note that
unsolicited messages from RTUs in half-duplex mode cannot be supported reliably. Message processing time
includes sending a message over RS485, a packtimer and a turnaround time. 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.
Section 5.4.1.3
Broadcast RTU Polling
Broadcast polling allows a single host-connected server to distribute a polling stream to a number of remote
Remote Terminal Units (RTUs).
The host equipment connects via a serial port to a server. Up to 64 remote servers may connect to the host
server via the network.