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Checking Data Link Status Section 5-4
Processing Data Only when Operation Is Normal Using the IL-ILC and JMP-JME Instructions
Perform processing only when operation is normal by creating a program
based on program blocks that process data for each node with the IL-ILC and
JMP-JME programs.
“Data Link Normal Operating Flags” can be created using the programming
described in
5-4-5 Error Detection Program Example.
Writing 0000 in the Data Link Area when Errors Occur
When data links are not operating normally, write 0000 to the data link area of
the node with the error to stop other data being received.
As an example, the following example shows how to write 0000 in the data link
area of node 2 (D00100 to D00120) using the BSET (block set) instruction
when an error occurs at node 2.
■ Data Link Example: Communications Error at Node 2
■ Example of Programming for Node 1 to Handle Communications Errors at
Node 2
Insert the above programming at the start of the program.
“Data Link Normal Operating Flags” can be created using the programming
described in
5-4-5 Error Detection Program Example.
Note 1. If an error occurs and 0000 is written to the Data Link Area occurs for an
unstable transmission path (i.e., one that repeatedly alternates between
communications errors and normal operation), the normal data will be fre-
ILC
IL
Node A Data Link
Normal Operation Flag
Node A data processing
ILC
IL
Node B Data Link
Normal Operation Flag
Node B data processing
ILC
IL
Node C Data Link
Normal Operation Flag
Node C data processing
Node 1
Node 2
Node 1
Node 2X
Node 1
Node 1 Node 2 Node 62
Node 2
Node 62 Node 62
Node 62
Node 2 Data Link
Normal Operation Flag
0000 is written continuously
in node 2's area (D00100 to
D00120) until node 2's flag
turns ON.
BSET
#0000
D00100
D00120