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Glossary
NI-VXI User Manual G-2 © National Instruments Corporation
address modifier One of six signals in the VMEbus specification used by
VMEbus masters to indicate the address space and mode
(supervisory/nonprivileged, data/program/block) in which a data
transfer is to take place.
address space A set of 2
n
memory locations differentiated from other such sets in
VXI/VMEbus systems by six signal lines known as address modifiers.
n is the number of address lines required to uniquely specify a byte
location in a given space. Valid numbers for n are 16, 24, and 32.
address window A range of address space that can be accessed from the application
program.
ANSI American National Standards Institute
ASCII American Standard Code for Information Interchange. A 7-bit
standard code adopted to facilitate the interchange of data among
various types of data processing and data communications equipment.
ASIC Application-Specific Integrated Circuit (a custom chip)
asserted A signal in its active true state.
asynchronous Not synchronized; not controlled by periodic time signals, and
therefore unpredictable with regard to the timing of execution of
commands.
ASYNC Protocol A two-device, two-line handshake trigger protocol using two
consecutive even/odd trigger lines (a source/acceptor line and an
acknowledge line).
B
backplane An assembly, typically a PCB, with 96-pin connectors and signal paths
that bus the connector pins. A C-size VXIbus system will have two
sets of bused connectors called the J1 and J2 backplanes. A D-size
VXIbus system will have three sets of bused connectors called the J1,
J2, and J3 backplane.
base address A specified address that is combined with a relative address (or offset)
to determine the absolute address of a data location. All VXI address
windows have an associated base address for their assigned VXI
address spaces.