Omega 1002 User Manual download pdf (Page 34)

3.2.2.8.2 Trigger Method Selection

There are several trigger methods that can be selected by the user (see

section 1.4.5):

[Bit1,Bit0 ] Descriptions

[ 0, 0 ] General trigger mode.

8254 timer 0 trigger (internal pacer trigger ) or software

trigger.

[ 0, 1 ] External clock trigger mode.

[ 1, 0 ] Pre-trigger mode.

[ 1, 1 ] Post-trigger mode.

Note:

1. In the general trigger mode, both the 8254 timer 0 and the software

trigger are used as the A/D trigger signals. The timer 0 and the software

trigger should not be used at the same time! This means the user

should not generate a software trigger while the 8254 timer 0 is

activated!

2. In the external clock trigger mode, an external input is taken as the A/D

trigger signal. A single falling edge of the external trigger will generate

a single A/D trigger.

3. The pre-trigger mode employs the 8254 timer 1. The user should first

configure timer 1, then set the trigger mode to pre-trigger. Once the

pre-trigger mode has been activated, it will automatically turn on timer

1 and start the A/D trigger. This will continue until a falling edge from

an external trigger signal is received. Any change to the trigger mode

selection will turn off the pre-trigger mode.

4. The post-trigger mode employs the 8254 timer 1. The user should first

configure timer 1, then set the trigger mode to post-trigger. Once the

post-trigger mode has been activated, it will automatically turn off the

timer 1 until it receives a falling edge from an external signal. Any

change to the trigger mode selection will turn off the post-trigger mode.

5. The A/D trigger selection is set to 0 after power-on or hardware reset.

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Omega 1002 User Manual Page 34