Glossary
VXIpc-486 Model 500 Series
Glossary-2
© National Instruments Corporation
BIOS
Basic Input/Output System
block-mode
An uninterrupted transfer of data elements in which the master sources
transfer
only the first address at the beginning of the cycle. The slave is then
responsible for incrementing the address on subsequent transfers so that
the next element is transferred to or from the proper storage location.
BTO unit
Bus Timeout unit; a functional module that times the duration of each data
transfer and terminates the cycle if the duration is excessive. Without the
termination capability of this module, a Bus Master attempt to access a
nonexistent slave could result in an indefinitely long wait for a slave
response.
bus master
A device that is capable of requesting the Data Transfer Bus (DTB) for the
purpose of accessing a slave device.
byte order
How bytes are arranged within a word or how words are arranged within a
longword. Motorola ordering stores the most significant (MSB) byte or
word first, followed by the least significant byte (LSB) or word. Intel
ordering stores the LSB or word first, followed by the MSB or word.
C
C
Celsius
CLK10
A 10 MHz,
±
100 ppm, individually buffered (to each module slot),
differential ECL system clock that is sourced from Slot 0 and distributed
to Slots 1 through 12 on P2. It is distributed to each slot as a single-
source, single-destination signal with a matched delay of under 8 ns.
Commander
A Message-Based device which is also a bus master and can control one
or more Servants.
D
DMA
Direct Memory Access
DRAM
Dynamic RAM (random-access memory); storage that the computer must
refresh at frequent intervals.
dynamic
A method of automatically assigning logical addresses to VXIbus devices
configuration
at system startup or other configuration times.
dynamically
A device that has its logical address assigned by the Resource Manager.
configured device
A VXI device initially responds at Logical Address 255 when its MODID
line is asserted. A MXIbus device responds at Logical Address 255
during a priority select cycle. The Resource Manager subsequently
assigns it a new logical address, which the device responds to until
powered down.
