3-4
3.2 Setting the Basic Communication Area Between the
GT and PLC
3.2.1 What is the Basic Communication Area?
Communication between the GT and PLC is carried out as shown below.
As shown in the illustration, communication is carried out on an ongoing basis between the GT and
internal devices in the PLC. Internal PLC devices are divided into the following two devices:
Basic communication area
This area is for system control, such as screen switching settings. PLC devices belong to this area on a
fixed basis, and communication is constantly being carried out.
Breakdown of the basic communication area
• Word device: For reading devices handled in word units (3 consecutive words)
• Bit device: For reading devices handled in bit units (3 consecutive words)
References and output devices for parts
These are devices that are used in parts functions, and can be freely specified by the user.
Communication is carried out on an ongoing basis only for those that are currently displayed on the
screen and pertain to devices currently in use.
With the GT, before GTWIN screen creation tool is used to specify the devices for parts functions, the
“basic communication area” must be determined.
DT0 to DT2 and WR0 to WR2 are set as the default values for the basic communication area, but the
initial address can be changed using the following procedure.
Note:
The basic communication area should be used in the PLC ladder program to control the GT main unit.
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