Chapter 6: Concepts

Understanding Logic Analyzer Triggering

because timer1 will keep running and condition “Timer1 <500 ns” will never be met. There might be another rising edge on SIG1 that is followed within 500ns by the rising edge on SIG2 that occurs later on, so this situation is unacceptable.

To fix this problem, whenever the timer exceeds 500ns without triggering, the sequence should loop back to Level 1 to look for another rising edge on SIG1. The following shows an example of the correct sequence:

1.If there is a Rising Edge on SIG1, then Start Timer1

Go to 2

2.If there is a Rising Edge on SIG2 AND Timer1 < 500ns then Trigger

Else If Timer1 >= 500ns then

Reset Timer1

Go to 1

Occasionally, you may run out of timers. A counter can be used in place of a timer if the logic analyzer is sampling at regular intervals (that is, if it's in the timing sampling mode). A timer can be simulated by counting the number of samples that are acquired. For example, if the logic analyzer acquires a new sample every 10ns and seven samples are acquired, this represents 70ns.

Next: “Storage Qualification” on page 249

 

Storage Qualification

 

Storage qualification is used to determine if an acquired sample should

 

be stored (that is, placed in memory) or thrown away. This keeps the

 

logic analyzer memory from being filled with samples that are not

 

needed.

Default Storage

The simplest method to set up storage qualification is by setting up the

 

Default Storage. This is specified separate from the trigger sequence,

 

such as in a separate tab or another dialog. Default Storage means

 

“unless a sequence level specifies otherwise, this is what should be

 

stored”. As an example, you may want to only store samples if ADDR is

 

in the range 1000 to 2000, so you should set the Default Storage to:

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Image 249
Agilent Technologies 16760A manual Next Storage Qualification on, Needed, Default Storage, 249