Configuring Byte Order For Connection Via Serial Card - Emerson Rosemount 5708 3D Solids Scanner DeltaV Series Manual Supplement

Manual Supplement
00809-0300-4570, Rev BA
2.0

Configuring byte order for connection via serial card

Modbus
provides client/server communication between devices connected on different types of buses or
networks.
Modbus bases its data model on a series of tables that have distinguishing characteristics
http://www.Modbus.org
The four primary tables are:
Table 1-3. Modbus Data Model
Primary tables
Discrete Input
Coils
Input registers
Holding Registers
Since floating points and long integers (32-bit) are not embedded in Modbus, different methods have
been used to send and receive data. The most common used method for the transfer of extended data
types (floating point and long integers) is two consecutive 16-bit registers; however, the transmission
sequence of the registers is not fixed.
The Rosemount 5708 3DLevel device sends the Most–Significant Bit (MSB) in the first Modbus register
and the Less–Significant Bit (LSB) in the following register. Nevertheless, when DeltaV is set to read a
32-bit data register, it assigns the 16-bit world in the first Modbus register to the LSB data and the second
register to the MSB.
Figure 1-6. Modbus Word Order in Rosemount 5708 and DeltaV
Rosemount 5708 3D Solids Scanner
16-bit word
Register Low
(4000X)
16-bit word
The discrepancy described above shows that the parameter data is not read correctly by DeltaV.
Rosemount 5708 Series 3D Solids Scanner Integration with DeltaV
®
is an application layer messaging protocol, positioned at level 7 of the OSI model, which
Object type
Single bit
Single bit
16-bit word
16-bit word
MSB LSB
16-bit word
Register High
(4000X+1)
16-bit word
Modbus Data
Rosemount 5708 Series 3D Solids Scanner Integration with DeltaV
Type of Comments
Read-Only Can be provided by an I/O system
Read-Write Can be alterable by an application program
Read-Only Can be provided by an I/O system
Read-Write Can be alterable by an application program
MSB
16-bit word
Register Low
(4000X)
16-bit word
DeltaV
LSB
16-bit word
Register High
(4000X+1)
16-bit word
Modbus Data
2016
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