Profibus-dp interface description, General information, Data transfer structure – Baumer GK473 User Manual

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Manual_GK473_Profibus_EN.doc 9/16

Baumer IVO GmbH & Co. KG

04.05.11

Villingen-Schwenningen,

Germany

5. Profibus-DP interface description

5.1. General

information

The gateway provides the connection between the SPA’s RS 485 protocol and the Profibus-DP.

The Profibus-DP interface is in line with Profibus standard DP-V0 (cyclic communication) according
DIN EN 50170. Possible transmission rates are 9600, 19200, 93,75k, 187,5k, 500k, 1.5M, 3M, 6M and
12M Baud. The baud rate applied is recognised and set automatically.

Since there are no existing standards for gateway profiles they are manufacturer-specific.

5.2. Data transfer structure

The PLC output data to the gateway contain the complete command for the addressed SPA. The
command is added by tokens for start and stop as well as by the CRC check sum and passed by the
gateway via RS485. In the Profibus line the gateway has a firm length of 16 byte I/O data.

In direction vice-versa, the tokens for start and stop as well as the CRC check sum are removed from
the RS485 message, but latter is passed with unchanged content to the data block of a Profibus
message so that it is available at the PLC as consistent input data.

Furthermore, the gateway provides additional functions to relieve the upstream PLC and its program
editing.

To identify new RS485 telegrams, the Profibus telegram comprises an additional count byte that is
altered or better incremented with each new RS485 telegram.

Contrary to the RS485 protocol of the SPA, the Profibus data block has a firmly defined length of 16
byte. Basically it is consistently transferred in both directions and also has to be evaluated this way by
the PLC. Consistency means in this case that all bytes belong together and must not be separated.

The example below is showing how a „check position“ command is transformed from Profibus into
RS485 as well as the transformation of the RS485 response into Profibus.

The gateway is receiving the following, consistent data block from the PLC. The first 00h is serving as
footer token marking the end of the command so that its length can be recognised by the gateway. The
count byte zz was incremented in the PLC to activate reception in the gateway.

Zhl Adr Cmd

data

transmit

27h 43h 00h 00h

00h

00h 00h 00h 00h

00h

Now the SPA (address 7 = 27h) is getting the following command by the gateway:

SOH Adr Cmd EOT CRC

transmit

01h 27h 43h 04h 16h

In the SPA profile number 5 is active, the SPA is „in position“ (token „o“) SPA replies to gateway by

SOH Adr Cmd Stat. Profil-Nr=05 EOT CRC

response

01h

27h 43h 6Fh 30h

35h

04h

45h

The gateway transforms the response into the following consistent data block. The count byte is
incremented to release reception in the PLC.