Omron CP - PROGRAMMING MANUAL 05-2007 Programming Manual page 836

Basic I/O Unit Instructions
Precautions
Example
I/O refreshing will not be performed if a CPU Bus Unit Error (A402.07) or CPU
Bus Unit Setup Error (A402.03) has occurred in the specified CPU Bus Unit.
I/O refreshing will be stopped if an I/O Bus Error occurs while I/O refreshing is
being performed by DLNK(226).
DLNK(226) refreshes data between the CPU Unit and specified CPU Bus
Unit. Some time is required for the data exchange with the CPU Bus Unit (for
example, a data link with a Controller Link Unit).
If the specified CPU Bus Unit is exchanging data, DLNK(226) will not be exe-
cuted and the Equals Flag will be turned OFF. We recommend programming
the execution conditions shown below so that the execution of DLNK(226) will
be retried automatically.
Execution
condition
b
a
When CIO 0.00 is ON in the following example, DLNK(226) performs immedi-
ate I/O refreshing (in this case, data link refreshing within the PLC) for the
CPU Bus Unit with unit number 1 (in this case, a Controller Link Unit).If I/O
refreshing cannot be performed because the Controller Link Unit is refreshing
data, the Equals Flag will be turned OFF causing W0.01 to be turned ON so
that the instruction execution will be retried in the next cycle. When the I/O
refreshing is completed normally, the Equals Flag will be turned ON and the
instruction will not be retried in the next cycle.
W0.00
0.00
Equals Flag
W0.01
Equals Flag
DLNK
N
Equals Flag
a
Equals Flag
b
DLNK
&1
W0.01
W0.00
Section 3-22
803