BASI BUFM660 Series, Manual

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2) The slave response :
Address code + Function code + Data + CRC
(03H) (0AH+10 bytes data)

Address code : the address of the receiver. This parameter contains one byte of
information. In RTU mode it is coded with one hexadecimal byte, which is
corresponding to the decimal valid number (0-247).

Function code: the code is fixed “03H”, to send the value of the holding registers.

Data: the data has 11 bytes, “1 byte number of data ”and “10 bytes data”.
“1 byte number of data “ is “0AH”, which means the slave returns 10 bytes values.
“10 bytes data” is “3 bytes instantaneous flow rate” and “1 byte flow rate decimal point
position code” and “4 bytes accumulated flow rate” and “2 bytes level value”.

For example: the slave response as follow
“02H 03H 0AH 00H81H9DH 02H 00H00H0AH33H 01H8AH D5HF6H”.
“02H 03H 0AH” means: the No.2 address instrument answer the response from the
master, with its order to send the value of the holding registers with 10 bytes data.
“00H81H9DH” means the instantaneous flow rate is 00H81H9DH in hexadecimal, with
its decimal value “33311”;
“02H” means the decimal point position is 2 digits from the bottom, so the
instantaneous flow rate is 333.11, with its unit code same with its setting in
programming mode.
“00H00H0AH33H” means the accumulated flow rate in hexadecimal, with its decimal
value “2611”, the accumulated flow rate has one decimal point before the last digit, and
its unit is “M3”, so the accumulated flow rate is “261.1M3”.
“01H8AH” means the level value in hexadecimal, with its decimal value “394”, and its
unit is “mm”, so the level is 394mm.