Rockwell-automation 2711 MODBUS COMMUNICATIONS FOR PANELVIEW TERMINALS Manual do Utilizador descarregar pdf (Página 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

1 2 3 4 5 6 7 8 ... 23 24

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Rockwell-automation 2711 MODBUS COMMUNICATIONS FOR PANELVIEW TERMINALS Manual do Utilizador Página 3