QUANTUM
™
LX EVAPORATOR CONTROL PANEL
COMMUNICATIONS SETUP
090.610-CS (MAY 2016)
Page 35
SECTION 4
MODBUS
®
PROTOCOL
Changing a setpoint causes the Quantum™ to
save the new setpoint to nonvolatile memory.
Be careful not to continuously request a setpoint
change. Keeping the Quantum™ busy writing to
memory will interfere with the Quantum™ com-
municating to its I/O boards. A communication
failure to an I/O board will cause the Evapora-
tor to shutdown. For more detail and a list of
the data, reference the Quantum™ Data Table
section of this manual. For details about the ac-
tual protocol, reference the Modicon website at
http://www.modbus.com.
MODBUS® TCP/IP (Ethernet)
TCP/IP is the common transport protocol of the
Internet and is actually a set of layered proto-
cols, providing a reliable data transport highway
between Quantum™ LX panels and an Ethernet
network. Ethernet has become the standard for
factory networking, replacing many of the data-
bus systems used in the past.
MODBUS® TCP/IP simply takes the MODBUS®
instruction set and transparently wraps TCP/
IP around it. Unlike MODBUS® ASCII and RTU,
there no parameters that need to be set (such as
baud rate, data bits, etc.).
NOTE: When using Modicon Setup Software,
ensure that:
• Head number = Rack Position (position
of Ethernet card in its rack)
• Socket # = 502
Frick® Controls utilizes function codes 3 (Read),
6 (Write) and 16 (Multiple Write) of the TCP/IP
protocol. Use port 502 for Modbus TCP/IP com-
munications. The value used for the Modbus ID
must be greater than zero.
MODBUS® TCP LOG
MODBUS® Protocol
General Description
MODBUS® Protocol is a messaging structure de-
veloped by Modicon in 1979, used to establish
master-slave/client-server communication be-
tween intelligent devices. It is a standard, truly
open and the most widely used network protocol
in the industrial manufacturing environment. The
MODBUS® protocol provides an industry stan-
dard method that MODBUS® devices use for
parsing messages.
Since MODBUS® protocol is a messaging struc-
ture, it is independent of the underlying physical
layer. It is traditionally implemented using RS-
232, RS-422, or RS-485 communications hard-
ware. With the Quantum™ LX, MODBUS® TCP
can also be utilized as it applies to Ethernet net-
works.
The Quantum™ controller is setup to commu-
nicate on standard MODBUS® networks using
either ASCII (American Standard Code for Infor-
mation Interchange), RTU or TCP/IP.
The Quantum™ provides the capability to inter-
face with other devices that support serial data
communications using the MODBUS® protocol.
This is a Master / Slave multi-drop communica-
tion method whereby the Quantum™ is setup to
be a MODBUS® Slave. The customer’s PLC (Pro-
grammable Logic Controller) or DCS (Data Com-
munications System, such as a desktop or laptop
computer) must be setup as a MODBUS® Master.
The Master initiates the reading and writing of
data (queries) to a Quantum™. The Quantum™
does not generate its own data, it will only reply
to a request by the Master.
The Quantum™ ID number is used as the MOD-
BUS® Slave address (for ASCII and RTU). The
Master uses Function Code 3 (Read Holding Reg-
isters) to send a request to read data from the
Quantum™. The Master uses Function Code 6
(Load Register) to request to change a setpoint
or to send a command. Up to one hundred and
twenty-ve (125) data elements can be read with
one read request.
The address references are numbered rela-
tive to the Frick® addresses in the Quantum™
Data Table (see MODBUS Addressing Note in the
Quantum™ Data Table section of this manual for
additional information). The Quantum™ only ac-
cepts one value with a Load Register request.
To Next Page
Loading...
