Teledyne LeCroy USBTracer_Trainer - Users Manual - Manual (Page 305)

USB Protocol Suite User Manual Chapter 11: Traffic Generation (2.0)
LeCroy Corporation
291
11.5.1 Traffic Generation Modes: Bitstream vs. Intelliframe
IntelliFrame and Bitstream are modes that control how the generator interacts with
other devices when it is generating traffic.
•
Bitstream Mode - In Bitstream Mode, the generator constructs a bitstream of traffic
based on the UTG file and assumes that packets start at pre-calculated times. For
example, after an IN packet, the generator waits a calculated fixed time before pre-
senting an ACK. The time between them is determined by the idle= time statement
in between the IN and ACK packets in the .utg file. In this mode, every bit time of a
generation stream (including idles and SE0's) is represented by 4 bits of data, so the
file to be downloaded to the Generator can be very large.
• IntelliFrame Mode - In IntelliFrame mode, the generator can wait for Device
responses to complete before it continues generating more host packets. For exam-
ple, after issuing an IN, the generator looks for the DATAx packet issued by the
device to finish, and then issues an ACK. This way, the data length can vary and
does not need to be pre-calculated. Also, using the idle=TO_EOF statement allows
the generator to calculate where the end of the frame occurs, so that a subsequent
frame=AUTO statement creates a Start of Frame at the correct time. Moreover, the
Generator can be made to retry transactions that are NAKed automatically, and to
use the PING protocol where appropriate. Retries can be made to occur within the
same frame or in the next frame. For further information on the flexible behavior that
can be instituted during the generation, see the syntax descriptions for the genera-
tion files here. An additional advantage of the IntelliFrame mode is that it creates an
image in the Generator's memory that is MUCH smaller than that of the Bitstream
mode, so it downloads much faster.
Note: Device emulation only works in Intelliframe mode.
Note: In IntelliFrame mode, the hardware generates SOFs and Pings, so these
cannot be altered (force CRC value, explicit frame number, and so on). If you
want to explicitly corrupt or manage these PID types, you must use Bitstream
mode.
11.6 Starting Traffic Generation
To start traffic generation, click on the Tool Bar.
11.7 Repeating a Generation Session
If you wish to repeat a generation session, press the 
Traffic Generation Start/Stop button again. There is no need to reload the .utg file.
You can make an additional entry in a Generator Text File that allows you to specify a
portion of the file for repetition:
• Enter wrap=here in the Generator Text File.
The traffic above the entry is run only once. The traffic below the entry is repeated
continuously.
Note: For a usage example, see the sample file
FS_Enum_Break_Wrap_Sample.utg.
11.8 Stop Traffic Generation
To instruct the Analyzer to halt traffic generation:
• Click on the Tool Bar.