Measurement Computing PC104-DAS16JR/12 - Manual (Page 7)

1.4 DMA LEVEL SELECT
If using an XT PC there are only two DMA levels available and level 3 is probably
used by the hard disk controller. Set the DMA level switch to the level 1 position
(Figure 1-4). See Figure 1-1 or 1-2 for switch location.
If you have an AT or 386 type
computer the hard disk controller is
not at level 1 or 3 so either level may
be used.
There are other boards that use DMA
levels. Some network boards do and
so do some IEEE-488 interface
boards. If you have other boards in
your computer with DMA level
switches on them, make sure there are
no conflicts
Figure 1-4. DMA Level Select Switch
1.5 1 OR 10 MHZ CRYSTAL OSCILLATOR JUMPER
The 1/10 (1 or 10) MHz XTAL jumper selects the frequency of the source applied to
the on-board pacer. This pacer (counter 2) is used to pace the A/D start conversion
trigger (Figure 1-5). See Figure 1-1 or 1-2 for jumper location.
This jumper is on the board because the original DAS-16, designed in 1984, had a 1
MHz crystal. When MetraByte redesigned the DAS-16 and added the faster 10 MHz
crystal, a jumper was provided to maintain compatibility with older software.
The PC104-DAS16Jr/xx has the
jumper because the DAS-16 has the
jumper and some software requires
the jumper to be in the 1 MHz
position. However, some software
requires the 10 MHz position.
The PC104-DAS16Jr/xx is shipped
with the jumper in the 1 MHz
position. InstaCal allows you to
specify 1 or 10 MHz position in the
setup. See Figure 1-1 or 1-2 for
jumper location and orientation.
Note the difference in orientation in
Figures 1-1, 1-2, and 1-5.
Figure 1-5. Frequency Select Jumpers
3
M z H M z H
1
1 1 0
C IO -D A S 1 6 J R -1 2 C IO -D A S 1 6 J R -1 6
1 0
J 2