Endress+Hauser Cubemass DCI - Page 37

Cubemass DCI MODBUS RS485 Operation
Endress+Hauser 37
Data types
The following data types are supported by the measuring device:
• FLOAT (floating-point numbers IEEE 754)
Data length = 4 bytes (2 registers)
• INTEGER
Data length = 2 bytes (1 register)
• STRING
Data length = depends on device parameter,
e.g. illustration of a device parameter with a data length = 18 bytes (9 registers):
Byte transmission sequence
Byte addressing, i.e. the transmission sequence of the bytes, is not specified in the MODBUS
specification. For this reason, it is important to coordinate the addressing method between the
master and slave during commissioning. This can be configured in the measuring device by means
of the "BYTE ORDER" parameter (È "Description of Device Parameters" manual).
The bytes are transmitted depending on the option selected in the "BYTE ORDER" parameter:
FLOAT:
Byte 3 Byte 2 Byte 1 Byte 0
SEEEEEEE EMMMMMMM MMMMMMMM MMMMMMMM
S = sign
E = exponent
M = mantissa
Byte 1 Byte 0
Most significant byte
(MSB)
Least significant byte
(LSB)
Byte 17 Byte 16 to Byte 1 Byte 0
Most significant byte
(MSB)
to Least significant byte
(LSB)
Selection
Sequence
1st 2nd 3rd 4th
1 – 0 – 3 – 2 * Byte 1
(MMMMMMMM)
Byte 0
(MMMMMMMM)
Byte 3
(SEEEEEEE)
Byte 2
(EMMMMMMM)
0 – 1 – 2 – 3 Byte 0
(MMMMMMMM)
Byte 1
(MMMMMMMM)
Byte 2
(EMMMMMMM)
Byte 3
(SEEEEEEE)
2 – 3 – 0 – 1 Byte 2
(EMMMMMMM)
Byte 3
(SEEEEEEE)
Byte 0
(MMMMMMM)
Byte 1
(MMMMMMM)
3 – 2 – 1 – 0 Byte 3
(SEEEEEEE)
Byte 2
(EMMMMMMM)
Byte 1
(MMMMMMMM)
Byte 0
(MMMMMMMM)
* = Factory setting
S = sign
E = exponent
M = mantissa