1 profibus – Alicat PROFIBUS User Manual

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1.1 PROFIBUS

Alicat units can be optionally configured with a PROFIBUS communication

interface. PROFIBUS communications are done with telegrams. The following

is presented to an audience that is informed on the details of the PROFIBUS

specification. Details about connections and specifications are found in the

standard Alicat Operating Manual and on pages 10-11 of this bulletin.

1 GSD Configuration File

The latest GSD file can be downloaded from the Alicat website (www.

alicatscientific.com) or requested and sent via email. It is a text based document

that allows easy configuration of a PROFIBUS Alicat meter/controller onto a

PROFIBUS network. The GSD file takes precedence over this document in

any discrepancy.

2 PROFIBUS Operation

The PROFIBUS equipped unit does not have a termination resistor built in.

The user cabling must ensure that there is a terminator at the end of their bus.

Connection to a PROFIBUS unit is done through the female DB9 connector

on the top of the unit. This connector can optionally provide power to the unit.
There is a green LED on the top of the unit, it indicates if proper communication

is occurring. Upon connection to a bus, the unit goes through the following:

Auto Baud Rate Detect; optional Set Slave Address; Wait Parameterization;

Wait Configuration; and Data Exchange.

3 Auto Baud Rate Detect

At power up, a PROFIBUS equipped Alicat meter/controller will initialize its

PROFIBUS interface and enter baud rate detect mode. The unit supports all

standard baud rates given in the PROFIBUS specification. These baud rates

are listed in the GSD file. Once the baud rate is detected, the unit will be ready

to be parameterized or a new slave address can be set.

4 Set Slave Address

PROFIBUS equipped units, unless otherwise specified, are set at address

125. The address can be changed with the set slave address telegram as

specified in the PROFIBUS Specification. The customer can order PROFIBUS

unit(s) to be set at a different address from the factory.
The set slave address function can only be done before the unit has been

parameterized. After parameterization the unit will ignore set slave address

requests. The change of address is done immediately and it is stored into

nonvolatile memory.
Alternatively, the user can connect the unit to a serial port and change the

address which is stored in register 65. The details of reading and writing

note that an invalid address can be entered in this fashion and the user is

cautioned to use only addresses from 1-125.