Yaskawa SmartTrac DeviceNet Card - Manual (Page 40)

SMART TRAC DeviceNet Card
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Glossary of Terms Technical Manual 3554-0070
The lowest layer in the OSI seven-layer model. It concerns electrical and
mechanical connections and MAC. It is used by the data link layer. Example
physical layer protocols are CSMA/CD, token ring and bus
Communications messages, 8 bits at a time, used to send commands from
Master to Slave at specified time intervals and provide Slave response to the
Master.
A set of formal rules describing how to transmit data, especially across a
network. At a low level, a protocol defines the electrical and physical standards
to be observed, bit- and byte-ordering and the transmission and error detection
and correction of the bit stream. At higher levels, protocols describe data
formats, including the syntax of messages, handshaking (terminal-to-computer
dialogue), character sets and the sequence of messages, among other related
structures.
The way in which devices on a network are physically connected: star, bus, ring
or mesh. The topology may define transmission media, adapters, and physical
design of the network.
physical layer
Polled I/O
protocol
topology