Omron SYSMAC CS1W-CLK13 Operation Manual page 162

Checking Data Link Status
Note
Example of Programming for Node 1 to Handle Communications Errors
at Node 2
Node 2 Data Link
Normal Operation Flag
BSET
Insert the above programming at the start of the program.
Data Link Normal Operation Flags can be created using the programming
described in Using Data Link Communications Processing to Detect Normal
Operation or Errors in Other Nodes on page 136.
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-
quently cleared to 0000. Data processing methods that will not process
data or arithmetic operations when errors occur are recommended (such
as shown in the example for processing data only when data links are op-
erating normally or the example for processing data only when operation
is normal using the IL-ILC and JMP-JME instructions).
2. The BSET(071) instruction is used to write 0000 to the corresponding area
in which the ladder program is executing, but the value in the data link table
will be read if the words are being monitored from Support Software. This
enables peripheral servicing (i.e., for Support Software) to be executed af-
ter the CPU Unit has performed I/O refreshing (Controller Link Unit data
link refresh).
3. With Controller Link data links, if there is an error at the remote node
(source node), the previous data (i.e., data received immediately before
the error) continues to be stored in the data link receive area of the node
receiving the data. To clear the data in the receive area to 0 when an error
occurs, refer to the above example and include the appropriate program-
ming for clearing to 0.
4. Refresh processing for the data used in Controller Link data links is per-
formed between the Controller Link Unit and CPU Unit with every cycle.
Therefore, the above programming must be included at the start of the pro-
gram. This method of clearing to 0 can be used with CS1, and CS1-H CPU
Units as long as the DLNK(226) instruction is not used, and can be used
with CVM1/CV CPU Units as long as CPU execution processing is set to
synchronous processing. It cannot be used with CS1-H CPU Units if the
DLNK(226) instruction is used, or with CVM1/CV CPU Units if CPU execu-
tion processing is set to asynchronous processing. (This is because when
the DLNK(226) instruction is used with CS1-H CPU Units, or when asyn-
chronous processing is set for the CVM1/CV CPU Units, the refreshing of
data for data links is not synchronized with the instruction execution cycle.)
0000 is written continuously
in node 2's area (D00100 to
# 0 0 0 0
D00120) until node 2's flag
D00100
turns ON.
D00120
Section 5-4
139