KEYENCE N-400 - Manual (Page 122)

Chapter 6 PLC Link
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6
Real-time control
• To specify the flag area, use “0000” or “0001”.
• While the N-400 is writing the bar code data read by the BL series in the PLC’s
memory, the flag area is specified as “0001”.
• When data writing is completed, the flag area becomes “0000”. This indicates
that new data has been stored in the A+02 to A+258 addresses.
When the A+00 address is “0000”, the stored data is available.
Example 1
Normally, the A+00 address is set to “0000”.
While the N-400 is writing data, the flag area is “0001”. When the flag area
becomes “0000”, the data stored in the A+02 to A+258 addresses can be
processed.
Example 2
Normally, the A+00 address is set to “0001”.
When data writing is completed, the flag area becomes “0000”. The data stored
in the A+02 to A+258 addresses can then be processed.
Set the A+00 address to “0001” immediately after data processing is completed.
When the A+00 address becomes “0000”, this indicates that writing new data is
completed.
Note: When the BL series continuously reads bar codes, the real-time processing
mode may replace stored data with new data before the new data is processed in
the PLC. This prevent this, use the sequential processing mode.
Sequential processing
• To specify the flag area, use “0002” or “0003”.
• When the A+00 address is “0002”, new data can be stored.
• When data writing is completed, the flag area becomes “0003”, and new data
has been stored in the A+02 to A+258 addresses.
• After data processing is completed, set the flag area to “0002”. Writing new data
is impossible until the flag area is “0002.
• Data which cannot be stored in the specified areas is retained in the BL series’
transmission buffer. (
➮ For the capacity of the BL series’ transmission buffer, see
p. 63.) If the amount of retained data exceeds the buffer capacity, the buffer
overflow error occurs and the “OVER” code is stored in the corresponding area.
This area is used to send the trigger input signal to the BL series to start reading
bar code data.
You can set this area to “Used” or “Unused”, depending on the N400’s internal
setting. (
➮ See p. 41.) If you set this area to “Unused”, users can freely use it.
+01
Reading trigger area