14
IM 04L41B01-18E
Communication Considerations
About Communication Interval
Data Update
The DX data is updated in a scan interval. Even if a PLC accesses the data at shorter
intervals than the DX scan intervals, the data is updated only at scan intervals.
Communication Interval
A PLC should access the DX at intervals of 125 ms or longer.
* This is required to maintain compatibility with other protocols supported by the DX than
EtherNet/IP.
Access to Non-existent Data
If non-existent data is accessed, either of the following operations occur.
• 0 is read if non-existent data is read.
• Nothing is done if non-existent data is written.
When the DX Data Type Differs from the Data Type Specified in a Command
Each data on the DX has a fixed data type.
Data on the DX which includes special data accessed using the same data type is
transmitted unchanged. Data on the DX accessed using a different data has its data type
converted. The following explains the conversion rules:
Reading Data on the DX
DX
Data type to be specified in a command
Type
Data type INT16
INT32
FLOAT
Measurement
channel
INT16
The data is read without
change.
The data is converted into
INT32 (including special data).
The data is computed based on
the decimal point information set
in each channel.
*1
Computation
channel
INT32
There are limitations of
INT16.
*2
The data is read without
change.
The data is computed based on
the decimal point information set
in each channel.
*1
Communication
input data
FLOAT
The data is converted to
INT16.
The data is converted to INT32. The data is read without change.
External input
channel (for
reading)
INT16
The data is read without
change.
The data is converted into
INT32 (including special data).
The data is computed based on
the decimal point information set
in each channel.
*1
*1 Special data will have the following values:
Data
Value
+ Over
7f800000H
(+∞)
– Over
ff800000H
(–∞)
Skip
ff800002H
(Nan)
Error
ff800004H
(Nan)
INVALID
ff800005H
(Nan)
Burnout (Up)
7f800006H
(Nan)
Burnout (Down)
ff800006H
(Nan)
*2 The following values are used.
Data
Value
+ Over
32767
– Over
–32768
Skip
–32768
Error
–32768
INVALID
–32768
Less than -32768
–32768
More than 32767
32767
Other than the above
The data is read without change as INT16.
