Rockwell Automation 2711 MODBUS COMMUNICATIONS FOR PANELVIEW TERMINALS - Manual (Page 3)

Publication 2711-6.9
Modbus Communications for PanelView Terminals 3
Modbus protocol Modbus protocol links Modicon Programmable Controllers and
devices emulating Modicon Programmable Controllers in a wide
variety of applications. Modbus protocol defines a message structure
that controllers can use regardless of the network type over which
they communicate.
Modbus is a half-duplex, master-slave communications protocol. The
network master (PanelView) reads and writes coils and registers as if it
was a Modicon controller. Every device on a Modbus communication
link emulates the coils and registers of a Modicon Programmable
Controller. Modbus allows a host to read and write coils/registers and
obtain diagnostic information.
Modbus protocol allows a single master to communicate with a
maximum of 255 slave devices. The master device on a Modbus
network is not assigned an address.
Modbus PanelView
Terminals Modbus terminals are identified by a 14 at the end of the catalog
number, for example 2711-K9C14.
The Modbus terminals have:
•
Modbus communication port
•
RS-232 printer/file transfer port
In addition, each terminal is available with either:
•
AC or DC power
The characters L1 at the end of the catalog number designate a
terminal with DC power (e.g. -T9A14L1).