JUMO 701061, Описание интерфейса, Страница: 50 / 84

4 Data flow
22
Response: 140302 3230 A0F3 (CRC16 = xF3A0)
Float values When using Modbus, float values are processed in the IEEE 754 standard
format (32-bit), but with the difference that bytes 1 and 2 are swapped with
bytes 3 and 4.
Single float format (32-bit) according to standard IEEE 754
S = sign bit
E = exponent (complement to base 2)
M = 23bit normalized mantissa
Modbus float format
Example Request the float value from address 0x0035, when this address contains the
value “550.0” (0x44098000 in IEEE 754 format).
Request: 140300350002D6C0 (CRC16 = C0D6)
Response: 140304
80004409 6434 (CRC16 = 3464)
After the transmission from the device, the bytes of the float value must be
swapped accordingly.
Many compilers (e.g. Microsoft Visual C++) store the float values in the
following order:
Float value
Please check how float values are stored in your application. If necessary, the
bytes will have to be swapped accordingly in your interface program, after
they have been fetched from the paperless recorder.
SEEEEEEE EMMMMMMM MMMMMMMM MMMMMMMM
Byte 1 Byte 2 Byte 3 Byte 4
Modbus address x Modbus address x+1
MMMMMMMM MMMMMMMM SEEEEEEE EMMMMMMM
Byte 3 Byte 4 Byte 1 Byte 2
Address x Address x+1 Address x+2 Address x+3
MMMMMMMM MMMMMMMM EMMMMMMM SEEEEEEE
Byte 4 Byte 3 Byte 2 Byte 1