KEYENCE BL-700 Series - Manual (Page 127)

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Chapter 6 PCL Link
6
● Operating procedure
1. To trigger the BL-700 to start reading, set the +04 address to “1”.
2. When the BL-700 recognizes the +04 address, it returns a “0” to the +04 ad-
dress. The BL-700 then starts reading the data.
3. The BL-700 continues reading for the “one-shot signal trigger time” set at the
+06 address.
4. When the BL-700 has read all the bar codes, it writes the new data in A+05 to
A+69. If a reading error occurs, the BL-700 writes a reading error code in A+05
to A+69.
These areas are used to flag that the bar code data has been stored. The following
two methods are available depending on the application.
■ Real time control
•
To specify the flag areas, use “0” or “1”.
• While the BL-700 is reading and writing the bar code data in the PLC’s memory,
the flag area is set to “1”.
• When data writing is completed, the flag area becomes “0”. This indicates that
new data has been stored in the A+05 to A+69 addresses. When the A+00
address is “0”, the stored data is effective.
• When the interval of bar code reading with the BL-700 is shorter than that of
communication with the connected PLC, data that has not been written into the
specified area is retained in the BL-700 transmission buffer. (For the capacity of
the transmission buffer, see p.86.) If the amount of retained data exceeds the
buffer capacity, the entire contents of the buffer is cleared and an “OVER” code
is stored in the memory data area (A+05 to A+09). If a buffer “OVER” error
occurs, the BL-700 halts operation, but then restores operation once the
“OVER” code has been stored.
Example 1
Normally, the A+00 address is set to “0”.
While the BL-700 is writing data, the flag area is “1”. When the flag area becomes
“0”, the data stored in the A+05 to A+69 addresses can be processed.
Example 2
Normally, the A+00 address is set to “1”.
When data writing is completed, the flag area becomes “0”. The data stored in the
A+05 to A+69 addresses can be processed.
Set the A+00 address to “1” immediately after data processing is completed. This
enables the BL-700 to use the point at which the A+00 address becomes “0” as the
trigger for writing new data.
Note: When the BL-700 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. To prevent this, use the sequential processing mode as shown below.
■ Sequential processing
•
To specify the flag areas, use “2” and “3”.
• When the A+00 address is “2”, new data can be stored.
• When data writing is completed, the flag area becomes “3”, and new data has
been stored in the A+05 to A+69 addresses.
A+00 (A is the head address in which the data specified in +00 to +03 is stored.)
Memory data flag areas