Endress+Hauser MODBUS RS485 User Manual

Proline Promag 53 MODBUS RS485 Operation
Endress+Hauser 67
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 SEQUENCE" parameter (see "Description of Device Functions" manual).
Depending on the selection in the "BYTE SEQUENCE" parameter, the bytes are transmitted as
follows:
FLOAT
INTEGER
STRING
Illustration using the example of a device parameter with a data length of 18 bytes.
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
Selection
Sequence
1st 2nd
1 - 0 - 3 - 2 *
3 - 2 - 1 - 0
Byte 1
(MSB)
Byte 0
(LSB)
0 - 1 - 2 - 3
2 - 3 - 0 - 1
Byte 0
(LSB)
Byte 1
(MSB)
* = Factory setting
MSB = most significant byte
LSB = least significant byte
Selection
Sequence
1st 2nd … 17th 18th
1 - 0 - 3 - 2 *
3 - 2 - 1 - 0
Byte 1 Byte 0
(LSB)
…Byte 17
(MSB)
Byte 16
0 - 1 - 2 - 3
2 - 3 - 0 - 1
Byte 0
(LSB)
Byte 1 … Byte 16 Byte 17
(MSB)
* = Factory setting
MSB = most significant byte
LSB = least significant byte

Endress+Hauser MODBUS RS485 Specifications

General

Brand	Endress+Hauser
Model	MODBUS RS485
Category	Measuring Instruments
Language	English