Chapter 5
Theory of Operation and Register-Level Programming
5-8
©
National Instruments Corporation
When operating stand-alone, the MIO board selects a new input channel
after each A/D conversion. A clock signal, SCANCLK, is generated by the
MIO board and starts each A/D conversion on the rising edge of the signal.
This clock also increments the onboard scanning counter. When a single
AMUX-64T board is connected to the MIO board, four AMUX-64T input
channels must be scanned for every MIO board channel. SCANCLK
increments the AMUX-64T scanning counter on every A/D conversion,
and Counter 1 on the MIO board must be used to divide the onboard
scanning counter clock by four. The Single-Board Configuration section of
Figure 5-5 shows the scanning order for the four AMUX-64T channels
multiplexed to MIO board channel 0.
If two AMUX-64T boards are attached to the MIO board, eight
AMUX-64T channels must be scanned for every MIO board input channel.
For example, channels 0 through 3 on AMUX-64T board A and channels
64 through 67 on AMUX-64T board B are multiplexed together into MIO
board channel 0. The Two-Board Configuration section of Figure 5-5
shows the order in which these eight AMUX-64T channels are scanned.
Observe that the first four channels on board A are scanned first, followed
by the first four channels on board B.
If four AMUX-64T boards are attached to the MIO board, 16 AMUX-64T
channels must be scanned for every MIO board input channel. For example,
channels 0 through 3 on AMUX-64T board A, channels 64 through 67 on
AMUX-64T board B, channels 128 through 131 on AMUX-64T board C,
and channels 192 through 195 on board D are multiplexed together into
MIO board channel 0. The Four-Board Configuration section of Figure 5-5
shows the order in which these 16 AMUX-64T channels are scanned: the
first four channels on board A are scanned first, followed by the first four
channels on board B, the first four channels on board C, and finally the first
four channels on board D.
