2.3.2. Functionality example
In the following example, there are two independent SCADA devices connected to RipEX's two COM
ports. One is designated RTU (Remote Telemetry Unit) and is assumed to be polled from the centre
by the FEP (Front End Processor). The other is labelled PLC (Programmable Logic Controller) and is
assumed to communicate spontaneously with arbitrary chosen peer PLCs.
Step 1
FEP sends a request packet for RTU1 through COM2 to
its connected RipEX.
Simultaneously PLC2 sends a packet for PLC1 to RipEX2
through COM1.
Step 2
FEP’s RipEX transmits an addressed packet for RTU1 on
Radio channel.
RipEX1 receives this packet, checks data integrity and
transmits the acknowledgement.
At the same time packet is sent to RTU1 through COM2.
RipEX3 receives this packet too. It doesn’t react, because
this packet is directed to RipEX1 only.
Step 3
RipEX2 waits till previous transaction on Radio channel is
finished (anti-collision mechanism).
Then RipEX2 transmits on Radio channel the addressed
packet for PLC1.
RipEX1 receives this packet, checks data integrity and
transmits acknowledgement.
At the same time packet is sent to PLC1 through COM1.
Simultaneously the reply packet from RTU1 for FEP is re-
ceived on COM2.
Step 4
RipEX1 transmitts the reply packet from RTU1 for FEP on
Radio channel.
All RipEXes receive this packet. This packet is addressed
to FEP’s RipEX, so only FEP’s RipEX reacts. It checks
data integrity and transmits the acknowledgement to
RipEX1.
At the same time the packet is sent to FEP through COM2.
RipEX Radio modem & Router – © RACOM s.r.o.
18
RipEX in detail