User manual

Glossary
VXI-MXI-2 User Manual Glossary-2 © National Instruments Corporation
A24/A32 Decoder The logic circuit on the VXI-MXI-2 that is responsible for
detecting data transfers to the module’s registers or DRAM in
A24 or A32 address space.
A24 space VXIbus address space equivalent to the VME 16 MB standard
address space.
A32 space VXIbus address space equivalent to the VME 4 GB extended
address space.
ACFAIL A VMEbus backplane signal that is asserted when a power
failure has occurred (either AC line source or power supply
malfunction), or if it is necessary to disable the power supply
(such as for a high temperature condition).
address Character code that identifies a specific location (or series of
locations) in memory.
address modifier One of six signals in the VMEbus specification used by
VMEbus masters to indicate the address space in which a data
transfer is to take place.
address space A set of 2
n
memory locations differentiated from other such sets
in VME/VXIbus systems by six addressing 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. In VME/VXI, because there are six
address modifiers, there are 64 possible address spaces.
address window A portion of address space that can be accessed from the
application program.
ANSI American National Standards Institute
arbiter Circuitry providing the bus arbitration mechanism for a system.
arbitration A process in which a potential bus master gains control over a
particular bus.
asynchronous Not synchronized; not controlled by time signals.