Measurement Computing CIO-DAS160x/1x - Manual (Page 8)

The input amplifier gain is controlled by a software programmed register located at BASE + B hex (11
decimal). The codes have different meaning for each board in the CIO-DAS1600 family. Refer to the
Register Architecture section for details on this register.
Figure 3-6. Bipolar/Unipolar Select Switch
3.7 PACER EDGE SELECT
The original Keithley MetraByte DAS-1600 was designed such that A/D conversion was initiated on the
falling edge of the convert signal. Neither the original DAS-16, nor any of the other DAS-16 derivative
converts on the falling edge. In fact, we are not aware of any A/D board that uses the falling edge to
initiate the A/D conversion.
When using the falling edge to start the conversion, the A/D may be falsely triggered by 8254 pacer clock
initialization glitching (easy to avoid but a real possibility in the DAS-1600). Converting on the falling
edge mode also may lead to timing differences if the CIO-DAS1600 board is being used as a replacement
for an older DAS16 series board.
Because using the falling edge trigger is undesirable, we have designed a jumper into the CIO-DAS1600
which allows you to choose which edge of the internal pacer signal
starts the A/D conversion. The jumper has no effect on an external
pacer signal (EXTCLOCK). The only reason we supply you the
option of a falling edge trigger is to provide complete compatibility
for those who have developed software for a DAS-1600 using the
AS-1600 drivers, AND, when using the CIO-DAS1600 with that
software you observe sample timing differences.
The CIO-DAS1600 is shipped with this jumper in the rising edge
position. Figure 3-7 to the right shows the edge selection options.
For compatibility with all third party packages, with all DAS-16
software and with CIO-DAS1600 software, leave this jumper in the
rising edge position
Figure 3-7. Trigger Edge Select Jumper
AUXILIARY TRIGGER
There is a position for a header connector at the rear of the CIO-DAS1600. This connector provides the
same function as that found on the DAS-1600.
The A/D trigger signal can come from this connector, if installed. A jumper controls which pin the
trigger signal comes in from. We do not install this connector (nor is it installed on the DAS-1600).
4
TRIGGER EDGE SELECT
JUMPER BLOCK
J9
J9
Falling Edge A/D Trigger
DAS-1600 Method
Rising Edge A/D Trigger
DAS-16 Method
Default
Setting