Specifications

7.2. Profibus settings

We will only be looking at the basic communication parameters of the protocol – other parameters

correspond to the standard Profibus DPV0. Profibus protocol is very sensitive to DP Slave response

times. Delays are common in radio networks; this should be taken into account when setting up

Profibus communication parameters.

Recommended default Profibus settings for data transfer using RipEX radio modems:

16 383 t_bitTslot_Init:

50 t_bitMax. Tsdr:

11 t_bitMin. Tsdr:

1 t_bitTset:

0 t_bitTqui:

Explanation of acronyms:

Tslot_init (Slot-time): This indicates how long a DP Master should wait for a response from a DP

Slave before it repeats a packet or sends another. The maximum value is 16 383.

Max. Tsdr (Maximum Station Delay of Responders): Sets the maximum DP Slave response time.

This value is the same for all DP Slaves and is distributed from the DP Master at the beginning of their

communication. This value must be lower than Tslot_init (Slot-time).

Min. Tsdr: Sets the minimum DP Slave response time. 11 to 255 bit values are permitted. This value

is the same for all DP Slaves and is distributed from the DP Master at the beginning of their communic-

ation. This value must be lower than Max. Tsdr.

Tset: Sets delay. This is used to postpone broadcasting of the next packet. This parameter enables

you to create space for other communication on RipEX network.

Tqui (Quit time): Sets the switching time between reception and broadcasting. This must be lower

than Min. Tsdr.

Note: All times are given in bits. 1 t_bit = 1 / Baud rate [seconds]

Baud rate – data transfer speedA single bit time

9600 bps104.2 μs

19200 bps52.1 μs

Example of Profibus DP settings in STEP 7

Under network layout click the right mouse button to open Object Properties:

Profibus