Leuze BCL34, Technical Description

Page: 53 / 102

PROFIBUS
Leuze electronic BCL 34 51
TNT
35/7-2
4
V
Example:
3 barcodes are to be transmitted. Accordingly, the parameter "number of barcodes" is set
to the value 3. After a reading gate activation (module 18) and the reading of 3 barcodes,
the first barcode is transmitted automatically. This barcode is available from the decoding
results module (module 21 - 27).
In the input byte "number of decoding results" of module 5, the BCL indicates that there
are still 2 decoded barcodes in the BCL's buffer memory. If the first barcode in the
controller has been processed or stored, the BCL receives an acknowledgement via the
output bit "acknowledge". This bit is a toggle bit, i.e., each edge transition ( 0->1 and 1->0)
is an acknowledgement.
The BCL now immediately tries to transmit the next barcode from the buffer memory. On
the one hand, the controller recognises the successful transmission by the change of the
input byte from 2 to 1, on the other hand, it is essential that the "new result" bit and the
associated toggle bit in the decoding results (module 21 -27) are evaluated. Only if a new
barcode is actually present in the decoding results and has been processed or stored, the
next acknowledgement should be carried out via the acknowledge bit. If this is not taken
into account, decoding results may be lost.
It is also important that all transmitted barcodes are really acknowledged. It is better to
acknowledge the last barcode one time too many than not at all. Otherwise, the buffer of
the device (module 20 -27) may overflow quickly.
Parameters
Input Data
Output Data
Parameter Description Rel.
addr.
Data
type
Value Range Default Unit CR to
module
Number of
barcodes
Number of different barcode types scanned for per
reading gate.
Only if this number of barcodes has been reached, the
reading gate is terminated prematurely.
1 … 20 1 –
20 or
21…27
5c
Parameter length: 1 byte
a
Input Data Description Rel.
addr.
Data
type
Value Range Default Unit CR to
module
Number of decoding
results
Number of decoding results which have not
been fetched.
0 unsign8 0 … 255 0 –
20 or
21…27
Input data length: 1 byte
b
Output Data Description Rel.
addr.
Data
type
Value Range Default Unit CR to
module
Acknowledge
Control bit signals that the data have
been processed by the master.
0,0 Bit
1 -> 0: Data has been processed
by the master
0 -> 1: Data has been processed
by the master
0 –
20 or
21…27
Output data length: 1 byte
c