Teledyne 2103c installation and operation guide Modbus Protocol, Operation

2103 Modem Module

Section 4 Modbus Protocol

	Sections 4.1 through 4.5 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 4.4
	and 4.5.
	For Modbus technical specifications, turn to section 4.6.
4.1 Introduction	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. There are three standard protocols for Modbus:
	Modbus RTU, Modbus TCP/IP, and Modbus ASCII. The Isco 2100
	Series devices use Modbus ASCII protocol, the method discussed
	in this manual. Modbus ASCII has more flexible communication
	timing requirements. 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 computer for display, data collection, or process control.
	Modbus 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.
4.2 Operation	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
	register locations. A list of the 2100 register addresses, and what
	parameters are held where, is available in section 4.6.

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