Balluff BIS C-6 0 RS 232 Serie Handbuch Seite 44

C-6_0-007-00_836905_E_0704.p65
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Dialog mode
Direct read mode
Protocol sequence
with schematic
representations
10
Data checking
10 english
Application
BIS C-6_0 Processor
The processor writes data from the host system to the data carrier and reads it from the data
carrier through the read/write head, and prepares it for the host system. Host systems may be:
– a controlling computer (e.g., industrial PC) or
– a programmable logic controller (PLC)
Depending on the configuration, the processor sends the read data carrier data to the host
unit after recognizing a data carrier.
The processor controls and adminsters the data communication between data carriers and
read/write heads. The serial port connects the BIS C-6_0 identification system to the external
controller.
Data is exchanged between the processor and the host system using specific telegrams.
The protocol sequence is represented in the form of function blocks on pages 32/33. See the
chapter on Programming Information for more details on the telegram contents.
Application
BIS C-6_0 Processor
When sending data between the read/write head and the data carrier a procedure is required
for recognizing whether the data were correctly read or written.
The processor is supplied with standard Balluff procedure of double reading and comparing.
In addition to this procedure a second alternative is available: CRC_16 data checking.
Here a test code is written to the data carrier, allowing data to be checked for validity at any
time or location.
Advantages of CRC_16
Data checking even during the non-active phase
(CT outside read/write head zone).
Shorter read times since each page is read only
once.
Since both variations have their advantages depending on the application, the user is free to
select which method of data checking he wishes to use (see Configuration on pages 13/16).
To use the CRC check method, the data carriers must be initialized. You use either data
carriers with the data map factory configured (all data are 0), or you must use the processor to
write the special initialization command 'Z' to the data carriers (see page 52).
It is not permitted to operate the system using both check procedures!
english
Advantages of double reading
No bytes on the data carrier need to be
reserved for storing a check code.
Shorter write times since no CRC needs to be
written.
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