Dwyer UXF3 - Manual (Page 16)

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5.5 Calculation of Error Check Code (CRC-16)
CRC-16 is the 2-byte (16-bits) error check code. From the top of the message (station No.) to the end of the data
field are calculated.
The slave station calculates the CRC of the received message, and does not respond if the calculated CRC is
different from the contents of the received CRC code.
Fig. 5-3 shows the flow of the CRC-16 calculation system.
NO
NO
YES
YES
NO
YES
Start
Set FFFF
H
(hexadecimal number) in CR.
Set 1 in I.
Exclusive logical sum (XOR) is executed
with CR and one character (1 byte) of the I
characters, and the result is set in CR.
Set 1 in J.
Bit at right end
of CR is 1?
Shift CR to right by 1 bit, and A001
H
and
exclusive logical sum (XOR) are executed
and the result is set in CR.
Shift CR to right by 1 bit.
Add 1 to J.
Calculation (8 times)
is finished?
J>8
Add 1 to I.
End
Explanation of variables
CR
:
CRC error check data (2 bytes)
I : Digits of calculation characters
in command message
J : Check on the number of times
of CR calculation
(Calculation is executed in the order
of command message station No.,
function code and data.)
CR calculation result shall be added
to the last command message in the
order of LOW byte and HIGH byte.
Calculation of all characters is
completed?
I>All characters
Fig. 5-3 Flow of CRC-16 calculation
Bulletin F-107-UXF3-S