Specifications

Fig. 7.2: ACK Off

Router mode should only be used where network topology

does not allow for Bridge mode to be used (see page YY of

the manual). If you choose to use Router mode we recom-

mend switching off acknowledgement on the radio channel.

This speeds up packet transmission on the radio channel.

Repetition of undelivered packets is ensured through the

application layer of the DP Master.

7.3.2. COM 2

Profibus DP utilises RS485 interface. This interface can only

be set to COM2 in RipEX. COM2 functionality is conditioned by using the appropriate software key,

see chapter Maintenance

of the manual.

COM2 settings must correspond to PLC device settings. We recommend setting port speed to 9600

for complex networks or 19200 bps for networks without re-translation (the timing is derived from the

length of a single bit).

Idle state can be reduced to as little as 1.

In Router mode, set Protocol to Profibus.

For explanation of the individual parameters refer to on-line help in the web interface or chapter Settings

of the manual.

Note: If Profibus IP's do not correspond to RipEX IP's (e.g. several PLC Slaves are connected to a

RipEX over a single bus), addresses must be translated using a table.

7.4. Advanced settings

7.4.1. Calculation of minimum slot time

Setting the appropriate (minimum) Tslot_Init value for a given network may significantly shorten the

total DP Slave polling cycle. If one of the DP Slaves is out of order or if its response is lost, the DP

Master will only wait for a set minimum time before sending another query. The value should be set to

maximum to prevent problems.

The calculator on http://www.racom.eu/eng/products/radio-modem-ripex.html#calculation enables you

to calculate the RTT (round trip time).

Set the PLC Master to Ethernet interface in the calculator (Profibus protocol timing is based on the last

sent byte; time on Master's RS485 does not figure in this calculation).

RTT for Bridge mode can be used directly; for Router mode the resulting average RTT needs to be

multiplied by constant 1.25 to receive the maximum achieved RTT.

Calculate the recommended Tslot_Init as follows:

Tslot_Init = RTT * (Port speed in bps) / 1000

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Profibus