Filter
Top Products
226 Modbus communication
Section 6: Meter operation Reference, Installation, and Operations Manual
June 2013 3-9000-743 Rev S
6.4 Modbus communication
The Mark III meter supports ASCII and RTU Modbus communication. For ASCII Modbus, both
7E1 and 7O1 are supported. For RTU Modbus, 8N1 is supported. The communication ports
provide automatic protocol detection - only the baud rate and Modbus ID need to be specified.
Refer to Section 5.2 for details on configuring the meter communication parameters.
Also, refer to the Daniel website:
http://www2.emersonprocess.com/EN-US/BRANDS/DANIEL/FLOW/Pages/Flow.aspx
for the current Modbus map file (Mark III Modbus Table 386K.xls), navigate to the following web
pages:
Flow Meters>Daniel Liquid and Gas Ultrasonic Flow Meters>Daniel Seniorsonic 4-Path Ultrasonic Flow
Meter>Documentation>Software Downloads>Software Updates
Flow Meters>Daniel Liquid and Gas Ultrasonic Flow Meters>Daniel Juniorsonic Gas Flow Meter>Docu-
mentation>Software Downloads>Software Updates
6.4.1 Mapping data points to Modbus Registers
The Mark III stores data in data points. The meter uses a Modbus map file to provide Modbus
access to the data points. The Modbus map file contains information that cross references the
Modbus registers with the associated Mark III data points and access units.
A different map file can be specified for each serial communication port. The default map file
configuration is Map.txt for Port A, Map1.txt for Port B, and Map2.txt for optional Port C;
however, at this time all the files are identical.
The Mark III maintains backward compatibility to Mark II Modbus registers whenever possible.
Mark III data points that do not map to Mark II Modbus registers have been assigned register
numbers outside of the range used by the Mark II. String-type data points are not accessible via
Modbus since Modbus does not support that data type.
For backward compatibility to the Mark II, Modbus registers within the range 1-9999 are always
read in metric units. All other registers (i.e., those numbered 10000 and above) can be read in
either U.S. Customary or metric units depending upon the selected meter units system. The
volumetric flow rate registers units also depend upon the selected volumetric flow rate time
unit. These selections are configured via the Daniel MeterLink
Field Setup Wizard - General page
(see Section 5.6.6).
For example, if the Mark III meter is configured for U.S. Customary units and volume-per-day,
then QFlow will be read via Modbus register 10624 in units of cubic feet per day.
For Modbus access information for a particular data point, consult
Daniel MeterLink online help. (There is a help topic for each data point. From Daniel MeterLink
click on Help, click on Mark III Registers Reference, select the Index tab, start typing the data
point name until the desired point is highlighted, and then click the Display button.)