Xycom XVME-560, Manual

Page: 38 / 70

XVME-560 Manual
September, 1984
3.7.4 External Trigger
Mode
The External Trigger mode will allow a low going pulse on pin 50 of connector
JK2
to
start a conversion. Figure 3-5 below shows the timing constraints.
100 nsec.
Rising edge
triggers
conversion
minimum
Figure
3-5. External Trigger Pulse
An alternate method
would
be to
have the
trigger line be normally low, then pulsed
high and back Iow again
as shown in Figure 3-6. This
is not the preferred method since
a conversion is started when the external trigger line is disabled after previously being
enabied.
Rising edge
triggers
conversion
Figure 3-6. Alternate External Trigger Pulse
Procedure
1)
Connect the External Trigger signal to pin 50 of JK2.
2)
Write the control word (base+81H) specifying mode bits
Ml
and MO as 1 and 1.
3) Specify the channel and gain by writing to the Channel/Gain register.
3.8 INTERRUPTS
The AIN can generate an interrupt to notify the host that the A/D conversion is
complete and that the data is valid. The level and vector generated by this interrupt
are both user-selectable.
The following four steps must be performed to generate an interrupt: