Setup guide

Chapter 2 System Objects
Object Reference Manual 3-58 www.Automationdirect.com
Note
Activating the Daniel option deactivates all Modbus holding register members (on
that device) except for 40001 – 49999 and 4000001 – 465000. If you attempt to read
D40001, for example, the returned value is 0, and Lookout
Direct
will not attempt to write
D40001 to the RTU. Of course, in devices that do not support this option, you can still read
and write two adjacent holding registers as a floating point value with the Modbus data
members F40001 – F4999. In fact, this is a more general purpose solution than the Daniel
option, because you can still read bits and word values out of the holding registers, too.
Some Modbus PLCs reverse byte order in a floating point data member. If
your process is returning garbled or senseless floating point values, select
the Modicon 32-bit floating point order (0123 vs. 3210) option in the
Advanced Modbus Options dialog box. This option chooses whether the
characters within the floating point registers (data members
F40001 –
F49999
and F400001 – F465000) are in little endian or big endian
format.
On occasion a Modbus PLC will direct
a message to your process. To poll
for all data member values following receipt of such a poll, select the Poll
on receipt of unsolicited message option in the Advanced Modbus
Options dialog box. Using this option is a way to force a poll of a Modbus
device based on an event, without reference to the configured poll intervals
and somewhat outside the usual Lookout
Direct
event-driven action.
Caution
Notice that the D and F data members read two adjacent registers as single,
32-bit numbers. One consequence of this is that if you connect to two adjacent registers,
such as
D40010
and
D40011
, you will get incorrect values because of overlapping. Make
sure that you do not connect to adjacent registers with the D or F data members.
Modbus Protocol Statistics
The driver monitors Modbus Protocol Statistics. This data is held within
readable data members of the Modbus object and you can see them in the
Modbus Protocol Statistics dialog box. To view the dialog box, select
Options»Modbus… and click on Statistics….
Note
The Options»Modbus… option is only visible in the Options menu if a Modbus
object was previously created in your Lookout
Direct
application.