Teledyne LeCroy Sierra M6-4 SAS_SATA Protocol Analyzer User Manual - Manual (Page 316)

Teledyne LeCroy Preferences
312 Sierra M6‐4 SAS/SATA Protocol Analyzer User Manual
3.18.5 Sampling Memory Usage Optimization
The Preferences dialog has a Sampling Memory Usage Optimization option in the Trace
Viewer tab. This Memory Assignment (MA) feature optimizes sampling memory
utilization.
If the Sampling Memory Usage Optimization Option is Checked
The system tries to use empty space in all memory banks to prevent any memory bank
from filling completely. Each physical link is not necessarily assigned to a specific memory
bank. The system can capture more sample data than if the MA option is unchecked, and
sample file size is closer to the user‐defined Sampling Memory Size.
Memory Assignment efficiency varies with Port Configuration and Trigger Position:
 FPGA: The Memory Assignment feature works for a pair of ports connected to
one FPGA, for example ports 1 and 2 (or ports 3 and 4). Memory Assignment
does not work for two ports connected to different FPGAs, for example ports 1
and 3.
 Triggering: Memory Assignment only starts after the trigger point. During 
pre‐trigger, each physical link is always assigned to a specific memory bank.
Post‐trigger, the system can try to use empty space in all memory banks, if you
check the MA option. Therefore, Memory Assignment efficiency is maximum
when Trigger Position is set to 0% (snap‐shot trigger) and is minimum when Trig‐
ger Position is set to 99% or when there is no triggering (you stop recording
manually).
 MUX: When MUX is enabled, each segment has four memory banks, limiting
Memory Assignment somewhat.
Here are examples of different Port Configurations and Trigger Positions:
 One port configuration (A ‐ ‐ ‐): Sample size is user‐specified sample size.
 Two port configuration (AA ‐ ‐): Ports 1 and 2 are on the same FPGA, so
Memory Assignment has an effect. If you use snapshot triggering, the sam‐
ple size is near specified size.
 Two port configuration (AA ‐ ‐): If you use manual stop,
Memory Assignment has no effect. Sample size depends on port traffic
loads.
 Two port configuration (AA ‐ ‐): If trigger is set at 50%, and there is enough
data to fill pre‐trigger, Memory Assignment has an effect. Sample size is typ‐
ically near specified size.
 Two port configuration (AA ‐ ‐): If trigger is set at 50%, but there is not
enough data to fill pre‐trigger, Memory Assignment has an effect. Sample
size is typically more than half specified size, with size determined by the
amount of data captured before trigger.
 Two port configuration (A ‐ A ‐): Ports 1 and 3 are not on the same FPGA, so
Memory Assignment has no effect. If one port has heavy traffic, it may fill its
memory bank and stop recording, resulting in smaller sample size than spec‐
ified.
Note: Checking this option does not affect the sample. It only allows larger sample sizes.