Connecting Methods - Omron NB-series Operation Manual

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Connecting Methods

RS-232C
RS-232C is a kind of serial physical interface standard formulated by Electric Industry Association
(EIA).
RS-232C method is based on 1:1 communication, which is applied to the point-to-point communication
within 15-meter distance due to the existence of common-ground noise and the unavoidable common-
mode interference etc.
RS-485
RS-485 uses the differential signal negative logic and the common 2-wire method, and the connectable
node on the same bus is up to 32. The master-slave communication method, i.e. one master
communicating with multiple slaves, is generally used in the RS-485 communication network.
RS-485 and RS-422A methods can realize 1:N communication, i.e. one host communicating with
multiple PLCs or PTs. The maximum number of PLCs or PTs that can be connected to the host is up to
32, and the maximum transmission distance is 500 meters.
RS-485 is half-duplex communication method that cannot allow the transmission and receiving to be
performed simultaneously.
RS-422A
It is unnecessary to control the data direction due to 4-wire RS-422A interface using separate
transmission and receiving channels. Any necessary signal exchange among the equipments can be
performed by using software method (XON/XOFF Handshaking) or hardware method (control wires).
RS-422A standard with its full name "Electrical Characteristics of Balanced Voltage Digital Interface
Circuits" specifies the characteristics of the interface circuit. Actually, there is also a signal ground, total
5 wires. Because the receiver uses high input impedance and the driving performance of the
transmission driver is more powerful than that of RS-232C, therefore the same transmission wire can
be connected with multiple receiving nodes, and the number of the connectable node is up to 10. That's
to say, one is the master and the others are the slaves. Due to the RS-422A which is impossible to
communicate between the slaves, therefore the RS-422A supports one-point-to-multiple full-duplex
communications.
Ethernet
Ethernet is a kind of baseband LAN specification, established by Xerox company and jointly developed
by Xerox, Intel and DEC companies, which is the most common communication protocol standard
adopted by the existing LANs. PT uses the standard UTP as the transmission media for the Ethernet.
The NB Series use UTP cables.
The network communications between PT and PLC can be realized through the Ethernet connection.
Connecting the PT and the PLC manufactured by OMRON through the Ethernet allows the data read
and written. What's more, connecting the PT with PC via the Ethernet can also perform the project
upload/download and the system processing.
NB-series Programmable Terminals NB-Designer Operation Manual(V106)
1 Introduction
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