Dynamic SFC3, Руководство оператора

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Dynamic Fluid Measurement SFC3 Liquid Pulse Manual Modbus Data
— 4-2
Date: 8/1/2019
FUNCTION CODE
To inform the slave device of what function to perform
FUNCTION
CODE
ACTION
01
03 Read Strings or Multiple 16 Bits
16 Write Strings or Multiple 16 Bits
ERROR CHECK
L R C MO D E
The LRC check is transmitted as two ASCII hexadecimal characters. First, the message has to be stripped
of the: LF, CR, and then converted the HEX ASCII to Binary. Add the Binary bits and then two's
complement the result.
C R C MO D E
The entire message is considered in the CRC mode. Most significant bit is transmitted first. The message is
pre-multiplied by 16. The integer quotient digits are ignored and the 16-bit remainder is appended to the
message as the two CRC check bytes. The resulting message including the CRC, when divided by the
same polynomial (X16+X15+X2+1) at the receiver, which will give zero remainder if no error, has
occurred.
EXCEPTION RESPONSE
Exception response comes from the slave if it finds errors in communication. The slave responds to the
master echoing the slave address, function code (with high bit set), exception code and error check. To
indicate that the response is notification of an error, the high order bit of the function code is set to 1.
EXCEPTION CODE DESCRIPTION
01 Illegal Function
02 Illegal Data Address
03 Illegal Data Value
BROADCAST COMMAND
All units listen to Unit ID Zero, and no one will respond when the write function is broadcasted.