Spirent SmartBits System, Reference Manual

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Glossary of Terms
Features and Terminology
264 SmartBits System Reference
Here you can see that 10 patterns of four bytes each can be edited to form the contents of
the VFD. The patterns are shown in alternating colors.
Each of the bytes of each pattern can be modified as needed. There is a tool bar menu item
Pattern that provides some basic
fill capabilities. Files containing data for the VFD can be
imported or saved via the File menu item.
The operation of VFD3 places pattern #1 into frame #1, pattern #2 into frame #2 and so
on. Once the end of the number of patterns is reached, the VFD begins back at the first
pattern and continues.
!
Caution: The VFD3 will not skip forward to the start of the next pattern or reuse the cur-
rent pattern. The next packet will start with the next untransmitted byte of the current pat-
tern. If VFD3 is used to control protocol information, generally this will not be a problem.
Collisions usually start during the preamble and continue for 96 bit times. This duration of
the collision would cover the MAC destination and source address, but not use any data
from VFD3. If however the VFD3 were used for MAC destination and/or source address-
ing, subsequent packets will be produced incorrectly after a collision.
VTEs
A term used in SmartWindow and SmartLib applications, VTE (Virtual Transmit Engine)
is a SmartBits engine that is fully customizable and generates its own "stream" of data.
VTE is synonymous with “stream.”