Balluff Inc BISC6XX Manual De Usuario

9

9

english

The processor writes data from the host system to the Data carrier or reads data from the
tag through the read/write head and prepares it for the host system. Host systems may
include:

– a host computer (e.g. industrial PC) or
– a programmable logic controller (PLC)

When sending data between the read/write head and the Data carrier a procedure is re-
quired for recognizing whether the data were correctly read or written.

The processor is supplied with standard Balluff procedure of double reading and compar-
ing. 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  

Advantages of double reading

Data checking even during the non-active phase
(CT outside read/write head zone).

No bytes on the data carrier need to be
reserved for storing a check code.

Shorter read times since each page is read only
once.

Shorter write times since no CRC needs to be
written.

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 Parametering on   26).

It is not permitted to operate the system using both check procedures!

☞

C60_2-019_818217_0806-e.p65

10

english

10

Communication between the BIS C-60_2 processor and the host system is via PROFIBUS-DP.

The PROFIBUS-DP system consists of the components:

In some control systems the PROFIBUS-DP data area is not synchronously transmitted with the
updating of the input/output content. If more than 2 bytes of data are sent, a mechanism must
be used which guarantees that the data in the PLC and the data in the BIS C are always identi-
cal!

1st alternative: Synchronous data transmission as a setting on the Master
In this method the bus Master ensures that all the data necessary for the respective Slave are
always sent contiguously. There is usually a special software function in the PLC which likewise
controls access between the PLC and bus Master so that data are always sent contiguously.

2nd alternative: Set 2nd bit header
Data exchange between PLC and BIS is controlled by the so-called bit header. This is always
the first byte of the respective read/write head in the data buffer. This bit header exists both in
the input range (data from BIS to the PLC) and in the output range (data from the PLC to the
BIS). lIf this bit header is also sent as the last byte, a comparison of these two bytes can be
used to guarantee the consistency of the transmitted data.

In this method the PLC cycle is unaffected nor is the bus access time changed. All that is
required is that a byte in the data buffer be used for the 2nd bit header instead of for user data.

☞