Chapter 5
Theory of Operation and Register-Level Programming
©
National Instruments Corporation
5-11
For example, if one AMUX-64T board is used, channels 0 through 3 on the
AMUX-64T are automatically scanned whenever channel 0 on the MIO
board is selected in the scan sequence. If two AMUX-64T boards are used,
channels 0 through 3 (board A) and channels 64 through 67 (board B) are
automatically scanned. If four AMUX-64T boards are used, channels 0
through 3 (board A), channels 64 through 67 (board B), channels 128
through 131 (board C), and channels 192 through 195 (board D) are
automatically scanned.
If the MIO board is programmed with a sequential channel scan sequence
(0 through 7 or 0 through 15), the AMUX-64T channels are scanned from
top to bottom in the order given in Table 5-3.
If only one AMUX-64T board is used, the channels are scanned in the order
0 through 63 for single-ended configuration. The scanning order becomes
complex only when more than one AMUX-64T board is used.
During interval scanning, the number of channels scanned during an
interval is four times the channel scan sequence for one AMUX-64T board,
eight times for two AMUX-64T boards, and sixteen times for four
AMUX-64T boards.
Programming Channel Scanning with the AMUX-64T
To program the MIO board to conduct a scanning operation with the
AMUX-64T, the following steps must be added to the instructions for
programming multiple A/D conversions with channel scanning given in
Chapter 4 of the user manual that came with your MIO board. These steps
can be added any time before initiating the A/D conversions.
Initialize the AMUX-64T Scanning Counter
The DOUTEN0 bit in the MIO board Command Register 2 (this bit has
different names depending on your MIO board) must be set in order to load
the AMUX-64T scanning counter.
To initialize the AMUX-64T scanning counter, use the following
programming sequence:
1.
Write 0 to digital I/O port A.
2.
Write to the External Strobe Register to load 0 into the AMUX-64T
scanning counter.
