Teledyne LeCroy PETracer EML Analyzer and Exerciser User Manual - Manual (Page 193)

PETracer EML User Manual Chapter 10: Traffic Generation
LeCroy Corporation
185
Chapter 10: Traffic Generation
PETrainer™ is a traffic generator that can emulate PCI Express™ root complexes and
endpoint devices. Traffic generation can be used to transmit known errors, allowing you
to observe how your device handles faulty link conditions.
After the PETrainer EML™ and DUT have been cabled and powered on, you can test the
setup by generating some traffic. The following steps show how to configure the
Exerciser to generate a Link Training sequence.
10.1 Theory of Operation
Overview
PETrainer offers two mechanisms for implementing traffic generation: scripts, in which
any type of traffic can be defined and executed, and the Generation Options dialog box,
which offers a collection of PCI Express specific behaviors that can be enabled for
automatic generation of traffic.
Using scripts, packets can be transmitted one after another or with certain timing or
event-based pauses between them. This allows the PETrainer to act as a pattern
generator with PCI Express-specific formatting and transmission rates. However,
creating traffic that emulates real devices with relatively complex protocol behaviors
using a simple pattern generator is quite complicated. Certain behaviors such as ACK
policies, and flow control require concurrent processing. This is where the automated
features of the PETrainer EML™ products become useful.
The PETrainer includes a collection of automated traffic generation circuits that
commonly exist in other PCI Express devices. These circuits include ACK/NAK
generation, flow control management, a Link Training and Status State machine
(LTSSM), replay buffers, and transaction timers. What makes the PETrainer unique and
so useful is that each of these behaviors can be individually modified or disabled. This
allows the user to perform operations that might not otherwise be possible using an off
the shelf PCI Express device. This can be particularly useful when doing compliance or
fault recovery testing.
Starting Point
When the PETrainer first powers up, it is at electrical idle on all lanes. The link is not
trained, but the Link Training and Status State Machine (LTSSM) is enabled and waiting
for a command to train the link. To begin communication with a PCI Express device, the
Link training must occur, but first the generation settings must be set. This involves
setting the Link parameters such as link width, polarity inversion, and lane reversal,
through the Generation Options dialog.
Note: Setting the options in the Generation Options dialog has no effect on the
PETrainer behavior until the first script is executed. In fact, each time a script
is executed, these behaviors are reprogrammed to the PETrainer and the
behaviors are modified accordingly.
The Link Connect toolbar button can then be pressed to signal to the LTSSM to initiate
Link training. Alternatively, a script can executed with the Link=L0 command.