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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 |
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