Chapter 6: Concepts

Understanding Logic Analyzer Triggering

edge before it begins looking for the next rising edge. Because there is a sequence of steps to find the trigger, this is known as a trigger sequence. Each step of the sequence is called a sequence level.

Each sequence level consists of two parts; the conditions and the actions. The conditions are Boolean expressions such as “If ADDR = 1000” or “If there is a rising edge on SIG1”. The actions are what the logic analyzer should do if the condition is met. Examples of actions include triggering the logic analyzer, going to another sequence level, or starting a timer. This is similar to an If/Then statement in programming.

Each sequence level in the trigger sequence is assigned a number. The first sequence level to be executed is always Sequence Level 1, but because of the Go To actions, the rest of the sequence levels can be executed in any order.

When a sequence level is executed and none of the Boolean expressions are true, the logic analyzer acquires the next sample and executes the same sequence level again. As a simple example, consider the following trigger sequence:

1. If DATA = 7000 then Trigger

If the following samples were acquired, the logic analyzer would trigger on sample #6.

Sample # ADDR DATA

11000 2000

21010 3000

31020 4000

41030 5000

51040 6000

6

1050

7000

<- This is where the logic analyzer triggers

7

1060

2000

 

In essence, Sequence Level 1 is equivalent to “Keep acquiring more samples until DATA=7000, then trigger”.

If a Boolean expression in a sequence level is met, another sample is always acquired before the next sequence level is executed. In other words, if a sample meets the condition in Sequence Level 1, another sample will be acquired before executing Sequence Level 2. This means that it is not possible for a single sample to be used to meet the conditions of more than one sequence level. Each sequence level can be thought of as representing events that occur at different points in

243

Page 243
Image 243
Agilent Technologies 16760A manual 243