Section 3 Modbus Protocol And 2100 Output; Introduction; Operation - Teledyne 2105 Installation And Operation Manual

2105 Interface Module

Section 3 Modbus Protocol and 2100 Output

3.1 Introduction

3.2 Operation

Sections 3.1 through 3.5 give an overview of the basic capabilities
and operation of Modbus protocol as it applies to Isco 2100 Series
flow modules.
For a Glossary of Terms and Common Acronyms, see Sections 3.4
and 3.5.
For Modbus technical specifications, turn to Section 3.6.
Note
The 2105 Interface Module is capable of receiving Modbus
input using ASCII or RTU protocol. For 2105 Modbus input
configuration, see Section 2.14 Modbus Input.
Modbus is a simple command/response mechanism to read from
and write to specific memory locations called registers. A register
is a holding place for a piece of digital information within the
equipment. For data output, the Isco 2100 Series devices use
Modbus ASCII protocol, the method discussed in this section.
Modbus ASCII has more liberal communication timing require-
ments. Modbus communication for the Isco 2100 Series provides
a standard protocol that can be used to retrieve real-time data
from a single module or stack of modules at a site, or multiple
sites, over a wide area. The data can be sent to a central com-
puter for display, data collection, or process control.
Modbus output implementation is independent of Flowlink and
cannot alter the Flowlink-programmed configuration of the
module. Modbus cannot be used to retrieve historical data from a
module's memory.
Due to the wide variety of configurations that can be made with
Modbus, it is impossible to cover every usable application. This
section will discuss the overall capabilities and operation of
Modbus.
There are many standard, third party Modbus drivers and OPC
servers that may be used to link a remote Modbus device, such as
a 2100 Series module, to SCADA or process control software,
such as Wonderware™ or Intellution™. The OPC server commu-
nicates with the remote instrumentation and accesses registers.
The definition of what information is contained and where (the
register number, or address) is decided by the manufacturer
(Teledyne Isco).
In a 2100 module, the registers hold, but are not limited to, the
current real-time value of the meter's level, velocity, flow, input
voltage, temperature, and total flow readings, stored in specified
3-1