3.2.2.8.2 Trigger method selection
Here’s a list of our trigger options (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 general trigger mode, both 8254 timer 0 and software triggers
are treated as A/D trigger signals. In this mode, 8254 timer 0 and
software trigger should not working at the same time!! This
means
users should not generate the software trigger while
8254 timer 0 is activated
!!
2.
In external clock trigger mode, external trigger input is taken as
the A/D trigger signal. If the external trigger input falls(falling
edge),will generate one A/D trigger.
3.
The pre-trigger mode is used for pre-trigger method. The mode is
incorporated with the 8254 timer 1. First, setup 8254 timer 1
properly. Then set the trigger mode to pre-trigger. Once pre-
trigger mode has been activated, the 8254 timer 1 will
automatically turn on and start to perform A/D triggers. It will
continue until the A/D trigger logic receives a falling external
trigger signal. Any change to the trigger mode selection will turn
off the pre-trigger mode.
4.
The post-trigger mode is used for post-trigger method. The mode
working incorporated with the 8254 timer 1. First, setup 8254
timer 1 properly. Then set the trigger mode to post-trigger. Once
post-trigger mode has been activated, the 8254 timer 1 will
automatically turn off until it receives a falling external trigger
signal. Any change to the trigger mode selection will turn off the
post-trigger mode.
5.
The A/D trigger is set to 0 after either power-on or hardware
reset.
PCI-1002 User’s Manual (Ver. 2.4, Mar./2004, PPH-015-24) ---- 32
