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4 Modbus protocol description
Double values The double values are also processed in the Modbus in the IEEE-754 standard
format (32bit). Unlike float values, bytes are not changed over for double
values.
Doupble-float format (32bit) as per IEEE 754standard
S - sign bit
E - exponent (two's complement)
M - 52bits normalized mantissa
Modbus double format
Example Request of the double value of address 0x0066, if value 1234567.89
(0x4132D687E3D70A3D in the IEEE-754 format) is written under this address.
Request: 140300660004A6D3 (CRC16 = D3A6)
Response: 1403084132D687E3D70A3DE1C1 (CRC16 = C1E1)
Please find out the way double values are saved in your application. After the
request from the paperless recorder, it might be necessary to change the
bytes over in the program you are using.
SEEEEEEE EEEEMMMM MMMMMMMM MMMMMMMM
Byte 1 Byte 2 Byte 3 Byte 4
MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM
Byte 5 Byte 6 Byte 7 Byte 8
Modbus address x Modbus address x+1
SEEEEEEE EEEEMMMM MMMMMMMM MMMMMMMM
Byte 1 Byte 2 Byte 3 Byte 4
Modbus address x+2 Modbus address x+3
MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM
Byte 5 Byte 6 Byte 7 Byte 8
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