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A-8 MS-Connect 210 User’s Manual

Interface Standards

Appendix E — Interface Standards

RS-232

RS-232 defines an interface between two devices such as, for example, the wiring box

and a host computer. It differs from the other interfaces by dedicating individual pins to

specific functions and by requiring both devices to share a common ground line. Since

both device chassis are connected to a common ground, a ground loop potential and the

possibility of noise interference exists. Therefore cable lengths are limited to a maximum

of 50 feet (15.24 m). Despite being the most limited, this interface is used frequently

because of the large installed base of RS-232 equipment.

RS-422

RS-422, unlike RS-232, measures signals deferentially; that is, the receiver looks at the

potentials between the two receive (or transmit) wires rather than the potential between

signal and ground. As a result, cables, if shielded, can be up to 4,000 feet (1,219m) in

length. Like RS-232, RS-422 communication is designed for only two devices on a single

line and must have a common ground. It can be used wherever RS-232 is used.

RS-485

RS-485, like RS-422, can transmit up to 4,000 feet (1,219 m) using differential voltages.

Unlike RS-422, its transmitters are turned off until a request for data is received from the

host. RS-485 is used exclusively in Multidrop configuration.

Ethernet

Ethernet is supported for 10/100M, TCP/IP, UDP, and EtherNet/IP. A 6-byte address is

used, which is divided into a 3-byte vendor ID and a 3-byte vendor-defined field. Ethernet

manufacturers are assigned a unique vendor ID, and are then responsible for insuring that

all of their devices have unique addresses in the last 3 bytes.

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Microscan MS-4X Manuel d'utilisateur Page 58