Anybus Communicator Modbus plus, Руководство пользователя

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Frame Objects 44
Doc.Id. SCM-1200-093
Anybus Communicator for Modbus Plus
Doc.Rev. 3.01
7.7 Checksum Object
Most serial protocols features some way of verifying that the data has not been corrupted during trans-
fer. The Checksum Object calculates and includes a checksum in a transaction.
Parameter Description
Error Check Start byte This parameter specifies the byte offset in the transaction to start checksum calculations on
Error Check Type
This parameter specifies which type of algorithm to use:
• CRC (2 bytes)
CRC-16 with 0xA001 polynome (Modbus RTU standard)
• LRC (1 byte)
All bytes are added together as unsigned 8-bit values. The 2’s complement of the result will
be used as a checksum.
• XOR (1 byte)
All bytes are logically XOR:ed together. The resulting byte will be used as a checksum.
• ADD (1 byte)
All bytes are added together as unsigned 16-bit values. The lowest 8 bits in the result will be
used as a checksum.
• AddInvASCII (2 bytes)
All bytes are added together as unsigned 8-bit values. The lowest 8 bits in the result are
inversed and used as a checksum, represented as hexadecimal ASCII (2 bytes).