D300529 0115 - BL67 I/O modules
12-31
BL67-1SSI
12.3 BL67-1SSI
The BL67-1SSI module is used for connecting SSI encoders with a maximum word length of 32 bits and
a maximum bit transmission rate of 1 Mbps. It provides a 24 VDC (500 mA) power supply. In order to
read SSI encoder data, the BL67-1SSI module outputs a clock signal with which the encoder value can
be read via the signal input. The clock signal and the signal input are based on the RS422 protocol.
12.3.1 Data transfer method
The BL67-1SSI module enables the SSI data to be transferred according to the requirements of the
application. An operational data transfer method can be set by the module’s parameters.
Gray code or binary code data
transmission is possible.
Bit transmission rates from 62.5 kbp
s to 1 Mbps are possible.
The SSI encoder value can be represented in a data frame with between 1 to 32 bits. Bits can be deacti-
vated at both the LSB and MSB side of
the frame. At the MSB side this is done by a masking operation,
which causes invalid bits to be set to 0. At the LSB side, the invalid bits are removed by shifting the
entire data frame to the right. The missing bits on the MSB side are filled with zeros.
12.3.2 Data exchange
The data transfer between the PLC to the SSI-module is cyclic. The cyclic data transfer from the PLC to
the SSI-mo
dule is done via the process output data, the cyclic data transfer from the SSI-module to the
PLC via the process input data.
The process output data is used for writing the registers and requesting data from them. It is possible
to stop the communication with the SSI encoder and activate or deactivate comparison operations.
The process input data is used for reading the contents of the registers inside the modules. In this case,
the SSI encoder value is part of the register. The writing of these registers can be controlled. The results
of different comparison operations can be supplied, and the communication status with the SSI
encoder can also be displayed. Status messages that were generated by the connected SSI encoder can
be passed to the PLC as process input data.
The diagnostics messages are also embedded in the process input data.
The parameter and diagnostics interface allows acyclic data to be transferred in addition to this cyclic
data. The parameters for the data transmission on the SSI module, such as bit transmission rate, tele-
gram length etc. are set via the parameter interface. The diagnostics interface supplies the higher level
system with error messages, such as parameter errors.
Process data
With PROFIBUS, PROFINET and CANopen, the I/O data of this module is localized within the process
data of the whole station via the hardware configuration tool of the fieldbus master.
With DeviceNet, EtherNet/IP and Modbus TCP a detailed mapping table can be created with the
TURCK configuration tool I/O-ASSISTANT (PACTware + BL67-DTM).
Process input data (PZDE)
The field input data is transferred from the connected field device to BL67-1SSI-module.
The process input data is the data that is transferred by the BL67-1SSI-module via a gateway to the PLC.
The transmission is realized in a 8-byte format which is structured as follows:
4 bytes are used for representing the data that was read from the register with the address stated at
REG_RD_ADR.
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