Specifications

Appendix C - Glossary of Terms RS-422 And RS-485 Applications Ebook
Page 114 of 137 Manual Documentation Number: <DocNumber>
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electrical interface. Gateways also solve other connectivity problems, like
allowing multiple “master” devices to access and share data.
Multidrop
Multiple devices at various locations connected in parallel or acting similar
to parallel devices.
A RS-485 network (Two-wire or Four-wire) with multiple devices in parallel
at various locations.
Multi-master protocol
A protocol that employs polling sequence breaks, to allow multiple devices to
request the bus or request service. Typically this is an empty time frame after
which a device may put its address on the bus, be acknowledged with a device
ID.
N
Node (RS-485)
Each driver/receiver pair on a RS-485 bus is a node on the network. Up to 32
nodes can be connected in parallel before adding a repeater. One repeater
equates to two nodes, one on each side.
Non-Isolated
A device or converter that has signal grounds or power sources in common
between the input and output sides or between the RS-232 and RS-
232/422/485 sides.
Null Modem
A null modem cable or connector permits two similar RS-232 Devices (wired as
DTE or DCE) to be connected together so that the outputs of one device are
routed to the inputs of the other device. At a minimum, the Transmit Data
(TD) of one device is routed to the Receive Data (RD) of the other, and the TD
of the second device to the RD of the other, and the ground lines are