Setup guide

Chapter 3 Driver and Protocol Objects
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Automationdirect.com 3-53 Object Reference Manual
Modbus
Modbus and ModbusMOSCAD are protocol driver classes Lookout
Direct
uses to communicate with equipment such as programmable logic
controllers (PLCs), remote terminal units (RTUs), or any other piece of
equipment using Modbus Serial (ASCII or RTU) or Modbus Plus
communication protocol.
The Modbus object class has general-purpose addresses, such as holding
register 40001, and is suitable for communicating with nearly all Modbus
devices, including the Control Microsystems TeleSAFE RTU.
The ModbusMOSCAD object class works with Motorola MOSCAD PLCs
and RTUs. It also uses the Modbus Serial (ASCII or RTU) or Modbus Plus
communication protocol, but its data members reflect the address of
Motorola MOSCAD devices.
You can limit the number of channels Lookout
Direct
uses on the SA-85
card by creating a
modbus.ini file in the Lookout
Direct
directory, as
shown in the following example.
[ALL]
MaxChannels=channel
where
channel
is a number between 1 and 8, inclusive (default = 8).
These protocol driver objects contain a great deal of data. All readable
and writable members (inputs/outputs), polling instructions, read/write
blocking, serial port usage, and so on are bundled with the object.
Therefore, as soon as you create a Modbus or ModbusMOSCAD object
you immediately have access to all the object data members (see data
member list in Table 3-12).
Note
LookoutDirect protocol driver objects automatically generate an efficient read/write
blocking scheme based on the inputs and outputs being used in your process file. You are
not required to build your own I/O blocking table.
As protocol drivers, both object classes conform to the specifications in
the Modicon Modbus Protocol Reference Guide PI-MBUS-300 Rev. C.
The drivers support ASCII and RTU transmission modes, as well as
Modbus Plus.