Glossary - Maretron N2KMeter User Manual

®
16 NMEA 2000

Glossary

®
Bandwidth: NMEA 2000 , like other serial networks, supports a certain number of bits per
second sent on the wire. The actual network traffic is reported as a percentage of the theoretical
maximum, and is called "% Bandwidth". The N2KMeter's measurements include bandwidth lost
due to bus errors and retries but most other diagnostic tools only include successful messages
in bandwidth calculations.
®
CAN: NMEA 2000 is based on a low-level network standard known as CAN or CANbus. Other
networks that use CAN include CANOpen, DeviceNet, and SDS. Although these networks are
based on CAN, physical layer and upper layer protocol differences limit the use of the N2KMeter
with these networks.
®
Frame Rate: NMEA 2000 messages are sent in one or more CAN message structures called
Frames. Frame Rate is the number of these structures sent in 1 second. Since one NMEA
®
2000 message may require several CAN frames, the frame rate is not necessarily the same as
the message rate.
®
Node Address: Each device on a NMEA 2000 network has a unique "Address", a number
between 0 and 255. This Address is known as the Node Address. The number is displayed in
hexadecimal notation on the N2KMeter display. Some network design specifications may refer
to node addresses with decimal notation. Please refer to the conversion table in Section 20 on
page 27 to convert between the two notations.
Noise: An undesirable intermittent voltage on a network signal or power wire.
P-P: Peak to peak measurements of varying voltage signals indicate the difference between the
minimum and maximum values within a specific interval.
Ripple: A regular, repeated deviation from the mean voltage of a power or signal conductor.
Terminator: 1) A resistor connected at the end of a transmission line (network cable) to prevent
®
signal reflections caused by impedance mismatches. NMEA 2000 requires two 120 ohm
®
terminators, one at each end of the network. NMEA 2000 terminating resistors also define the
recessive state of the network by ensuring that NET-H and NET-L return to zero differential after
a dominant bit.
Transceiver: A transceiver is a circuit (typically a chip) that converts digital bits to/from the
differential voltages on the network cable. Transceiver is a contraction of transmitter and
receiver.
Transient: A temporary deviation from the mean voltage of a power or signal conductor.
Page 24 Revision 1.3