Watlow Series SD Limit - Manual (Page 47)

6. Test the communications.
Once communications is configured, test the link to
the controller for verification that everything is wired
and configured properly. Check the wiring and configura-
tions if things aren’t working. One misplaced wire or one
incorrect setting will keep communications from work-
ing. When using an EIA-232 to EIA-485 converter, be
sure to follow the configuration instructions provided
with the converter, as some may require special
jumper/switch settings, external power supply require-
ments or special signals from the software. Some soft-
ware packages have built-in routines for testing the com-
munications or use Comm6 to help diagnose problems.
7. Start communications with the controller.
With the communications successfully verified, the
software is now ready for use with the controller. The
above guidelines are the general steps to establishing
communications with controllers using Modbus. Some
applications may require other steps not mentioned, but
would follow the same general process.
8. Programming and configuring the controllers.
When programming and configuring the controllers
with a software program, a couple of things must be kept
in mind. If the software allows changing Setup parame-
ters such as Input Type, other parameter values that are
dependent on that setting may be automatically
changed. Some software packages may warn you of this
possibility and others may not.
Also, some controllers require that any changes made
by the software program to controller parameters that
need to be retained in the controller memory must be
saved in the non-volatile memory writes register. Any
settings not saved to controller memory will be lost when
the controller’s power is turned off.
Writing to Non-Volatile Memory
The Series SD stores parameter values in non-volatile
EEPROM memory. This type of memory has a finite life
of approximately 100,000 write cycles. In some applica-
tions, you might need to constantly write new values to a
particular register. Examples might be the writing of
limit or alarm set points through serial communications.
Continuous writes may result in premature controller
failure and system downtime.
To prevent premature failure of the EEPROM when
frequently writing register values, write a 0 to register
17. Any values written after that, will not be stored to
EEPROM. However, this data is lost when power is re-
moved. Register 17 defaults to a value of 1 after each
power cycle, writing values to EEPROM again. You must
write a 0 to register 17 upon power up to prevent data
from being written to EEPROM.
Infrared Data Communications (IDC)
Infrared Data Communications is an option available
on the 1/16th, 1/8th and 1/4 Din Series SD products. This
option supports wireless communications with PDAs
(personal digital assistants) or other devices equipped
with infrared communications that support the IrDA 1.0
Standard. IrDA is an acronym for the Infrared Data As-
sociation, www.irda.org. A PDA or other master device
communicates with the SD Series using Modbus ASCII
via IRCOMM over IrDA. IDC supports wireless commu-
nications through transparent material to a distance of
no less than one meter between devices at a maximum
angle of 15 Degrees.
IDC can support complete Series SD parameter con-
figuration and operation. The actual user interface or
configuration is dependent on the master device (PDA)
application software. A source for this software is Instant
HMI from Software Horizons. For more information, go
to www.InstantHMI.com or call (978) 670-8700.
Advantages of this feature include automated logging
of key process variables, increased accuracy and ease of
use for recipe or configuration setups, and easier con-
troller data exchange in physically restricting environ-
ments, such as semiconductor clean rooms. This feature
reduces the use of paper to record instrument informa-
tion as well as human transposition errors.
Wa t l o w S e r i e s S D L i m i t ■ 4 5 ■ C h a p t e r 9 F e a t u r e s