5-2 Field Control™ Genius® Bus Interface Unit User’s Manual – October 1999 GFK-0825F
5
Configuring the Serial Bus Address and Baud Rate
Before a Bus Interface Un it can communicate on the Geniu s bu s, i ts serial bus address must be
configured. That mea ns if you install a Bus Interface Unit and power it up BEFORE co nf ig uring its
serial bus address, it does not communicate on the bus. When you subsequently configure the serial
bus address, the Bus Interface Unit begins communicating on the bus immediately. The baud rate
must be set first in order to configure the BIU online. See the instructions for setting on the Hand-
held Monitor on the next page.

Special Instructions for Series 90-70 PLC Systems

Assigning the serial bus address is the first configuration step, prior to assignm ent of the network
map for the Bus Interface Unit. So when the Bus Interface Unit starts communicating, its network
map has not yet been assigned. That causes the Series 90-70 PLC to generate CONFIGURATION
MISMATCH faults. One such fault appears for each non-matching data type and len gth .
Depending on the PLC's own configuration, CONFIGURATION MISMATCH faults may be either
diagnostic only, or “fatal" (shutting down the system).
To avoid probl em s, you can do e i th er of the follo wing (method A is preferred) :
A. Check the PLC configuration to determine whether CONFIGURATION MISMATCH is set up
as a fatal faul t. If it is, power ing up the bus an d Bus Interfa c e Un it then assi gn ing a serial bu s
address will cause a fatal error and shut down the PLC.
• If CONFIGURATION MISMATCH is a diagnostic fault, you can install the Bus Interface
Unit on the bus and power it up before configuring its serial bus address.
The Bus Interface Unit will start communicating immediately, generating
CONFIGURATION MISMATCH faults. Complete the configuration, i gn oring the fau lts
temporarily. When you complete the Bus Interface Unit configuration, the Bus Interface
Unit drops off the bus briefly, generating a LOSS OF DEVICE fault. When it returns, an
ADDITION OF DEVICE diagnostic appears. If no new mismatch faults occur after the
Bus Interface Unit comes back on the bus (check the timestamp on the faults), the I/O
.maps match in the PLC and in th e Bus Interface Unit.
• If CONFIGURATI ON MISMAT CH is a fatal fault, configure the Bus Interface Unit's
serial bus address and I/O map offline, before installing the Bus Interface Unit. HHM
setup instructions for offline configuration are on the next page. When you then install and
power up the Bus Interface Unit, CONFIGURATION MISMATCH faults will not be
generated. You can complete the rest of the configuration after installation and powerup, if
you prefer.
B. Take the BIU off the bus prior to configuring the Bus Interface Unit. Configure the Bus
Interface Un it baud rate, serial bus addr ess and network map while the BI U is off the bus.