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APPENDIX D
PCI-1712/1712L User’s Manual
Advantech Co., Ltd.
www.advantech.com
The write-only register of Write BASE+4 controls how the multiplexers
(MUXs) scan.
w Write BASE+4 bit 3 to bit 0, STR3 ~ STR0, hold the start scan
channel number.
w Write BASE+4 bit 11 to bit 8, STP3 ~ STP0, hold the stop scan
channel number.
Writing to the register automatically initializes the MUXs to the start
and stop channel. Each A/D conversion trigger also sets MUXs to the
next channel. With continuous triggering, the MUXs will scan from the
start channel to the stop channel and then repeat. The following
examples show the scan sequences of the MUXs (all channels are set
as single-ended).
Example 1
If the start scan input channel is AI3 and the stop scan input channel
is AI7, then the scan sequence is AI3, AI 4, AI 5, AI6, AI7, AI3, AI4,
AI5, AI6, AI7, AI3, AI4...
Example 2
If the start scan input channel is AI13 and the stop scan input channel
is AI2, then the scan sequence is AI13, AI14, AI15, AI0, AI1, AI2,
AI13, AI14, AI15, AI0, AI1, AI2, AI13, AI14...
The scan logic of PCI-1712/1712L card is pretty fancy and powerful,
you can set gain code, B/U and S/D by each channel. The scan logic
will be a little complex if you set the channel in differential mode. In
differential mode, the even channel (i.e. AI0, AI2, AI4...AI14) and odd
channel (i.e. AI1, AI3, AI5...AI15) are combined to one channel. The
odd channel is the positive end and the even one is negative end. For
example, if the AI0 is set as differential mode, then the AI0 and AI1 are
combined to one channel and refer to the gain code and B/U of AI0
(the AI1’s is useless). As the same rule, if the AI2 is set as differential
mode, then the AI2 and AI3 are combined to one channel and refer to
the gain code and B/U of AI2 (the AI3’s is useless). The following
examples show the scan sequence of differential mode.
Example 3
Suppose that the start scan input channel is AI2 and the stop scan
input channel is AI8. If AI2 is differential mode (D), AI4 is D, AI6 is D
and AI7 and AI8 are single-ended mode (S), then the scan sequence is
AI2, AI4, AI6, AI7, AI8, AI2, AI4, AI6, AI7, AI8, AI2, AI4...