User Guide

FS-8700-20 Profibus DP Driver Manual Page 16 of 22
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Appendix A. Special Driver Parameters
Appendix A.1. DP_Buffer
Within the Profibus DP card, the FieldServer can access data from two distinct buffers. The
Input buffer is the data that is sent from the slave to master. The Output buffer is the data
sent from the master to the slave. Each Map Descriptor specifies which one of these buffers
to access in the card.
DP_Buffer Description
Input Data to the master from a slave
Output Data from the master to a slave
Appendix A.2. Data_Type, Address & Length
Each Map Descriptor also specifies the Profibus DP data type. The data arrives from a
Slave or is sent from a Master as a sequence of bytes. By specifying the DP data type, the
driver knows how to interpret the bytes within the buffer. The supported types are Bit, Byte,
Word and Float. To indicate where in the buffer to access the data, the Address field is
used. For Byte, Word and Float type mappings, the address specifies the offset in bytes
from the beginning of the buffer. For Bit type mappings, the address specifies the offset in
bits from the beginning of the buffer. A bit offset of 0 would access the least significant bit in
the first byte in the designated buffer.
Data_Type Description
Bit Transfer Length bits to Data Array
Byte Transfer Length bytes to Data Array
Word Swap the bytes and transfer Length words to Data Array
Float Swap the bytes and transfer Length floats to Data Array