Glossary

Find definitions for technical terms in our Embedded Systems Glossary.

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Embedded Systems Glossary: N

NAK

(knack) n. A response that something was not received properly. Short for Not AcKnowledged. Ironically, the mere fact that there's a NAK implies that the packet or command was received. It could be that there was some sort of an error (possibly checksum related) or that the requested command was not supported.

nanosecond

n. A billionth of a second. Abbreviated ns. A nanosecond is the length of one clock cycle at a 1 GHz rate. In that sense, it is a relatively short interval of time in which the software in a more typical MHz/kHz embedded system cannot even begin to respond to events around it.

netlist

n. A computer file that lists all of the connections needed to produce a printed circuit board. The netlist is an ASCII text file that lists the characteristics of each component and what each pin of every component connects to. Each of these connections is called a node.

Netlists are produced by schematic capture programs and are sometimes used as inputs to autorouters.

netlist

A portion of a netlist showing that node N00002 is associated with both a resistor and a diode; these two components thus connect together

network processor

n. A device that is similar to a microprocessor, except that it has been optimized for use in applications involving network routing and packet processing. Abbreviated NPU. There is no standard architecture, but many network processors feature multiple RISC CPUs running in parallel. In this configuration, one central processor typically receives and handles network control packets while the others pass data packets through the system at network speeds. See also control plane, data plane. [more]

nibble

n. A 4-bit chunk of data. Any byte consists of an upper nibble and a lower nibble. This is a convenient unit of data precisely because it can represent one of 16 values. A single hexadecimal digit (0 through F) can represent the nibble in a data dump.

nonmaskable interrupt

n. An interrupt that cannot be disabled. Abbreviated NMI. Known as a trap (on some Intel processors), as a level 7 interrupt (Motorola), or by other names.

NVRAM

(en-vee ram) abbr. A type of RAM that retains its data even when the system is powered down. Short for Non-Volatile Random Access Memory. NVRAM frequently consists of an SRAM and a long-life battery. [more]