Alicat PROFIBUS - Manual (Page 3)

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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
register values are included in the standard Alicat Operating Manual. Please
note that an invalid address can be entered in this fashion and the user is
cautioned to use only addresses from 1-125.