Hardware Configuration and Installation
Chapter 2
VXI-AT2000/NI-VXI MS-DOS Getting Started
2-4
© National Instruments Corporation
Each switch in U31 (1 through 5) corresponds to one of the PC AT address lines (A5 through
A9). The first switch (1) corresponds to address line A5, the next switch (2) corresponds to
address line A6, and so on. The five least significant bits of the address (A4 through A0) are
used by the AT-MXI to select the appropriate AT-MXI register and cannot be changed;
therefore, bits A4 through A0 are always zeros when determining the base I/O address.
To change the base I/O address of the AT-MXI, press the side marked OFF to select a binary
value of 1 for the corresponding address bit. Press the ON side of the switch to select a binary
value of 0 for the corresponding address bit. Refer to Table 2-2.
Figure 2-2 shows two possible switch settings.
OFF
5
4
3
2
1
U31
Binary Hex
0
0
0
0
0
ON=0
ON=0
ON=0
OFF=1
ON=0
a. Switch Set to Base I/O Address hex 100
0
0
1
OFF
5
4
3
2
1
U31
Binary Hex
0
0
0
0
0
ON=0
OFF=1
ON=0
OFF=1
OFF=1
b. Switch Set to Default Setting
(Base I/O Address hex 340)
0
4
3
Figure 2-2. Base I/O Address Switch Settings
