Glossary
G-2
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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
VXI/VMEbus 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
arbitration
A process in which a potential bus master gains control over a
particular bus.
asynchronous
Not synchronized; not controlled by time signals.
B
B
Bytes
backplane
An assembly, typically a printed circuit board, 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 J1 and J2. A D-size VXIbus system will
have three sets of bused connectors called J1, J2, and J3.
BERR*
Bus error signal
binary
A numbering system with a base of 2.
BIOS
Basic Input/Output System. BIOS functions are the fundamental level
of any PC or compatible computer. BIOS functions embody the basic
operations needed for successful use of the computer’s hardware resources.
