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Programming Considerations Chapter 5
VXI-MXI User Manual 5-22 © National Instruments Corporation
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Size = 2
Size = 3
Size = 4
Size = 5
Size = 6
Size = 7
Size = 1
Size = 0
Figure 5-12. A16 Space Allocations for all Size Values
To plan the A16 address map, you will follow procedures similar to those for planning the
logical address space address map. Determine the amount of A16 space required by each device;
if you are using Base/Size windowing formats, round that amount up to the next address break
listed in Table 5-3. Next, assign the A16 space, starting with the root device and working down
the VXIbus/MXIbus system tree. To assist you in configuring the A16 window switches on the
VXI-MXI interfaces in your system, the following pages include worksheets, an address map
diagram, and an example.
The following steps are used in the example:
1. Identify the RM Mainframe and the MXIbus levels of your system. Determine the amount
of A16 space required by each MXIbus device. See Figure 5-12 and Table 5-4.
2. Fill out the RM Mainframe information in Figure 5-15, Worksheet 1. In this example, the
RM Mainframe needs 16 KB of A16 space, which rounds up to the next address break of
16 KB.
3. Next, analyze the first-level MXIbus links and complete a worksheet for each link. For our
example, we fill out Figure 5-16, Worksheet 2, for MXIbus #1, which includes MXIbus
Device A, MXIbus Device B, VXIbus Mainframe #2, and VXIbus Mainframe #3. MXIbus
Device A needs 512 B of A16 space, which rounds up to address break 512. We fill in the
worksheet accordingly. MXIbus Device B and VXIbus Mainframe #2 do not need any A16
space, so we put zeros in the worksheet for these devices. VXIbus Mainframe #3 needs 4
KB of A16, in addition to the amount of A16 required by MXIbus link #3 connected to it on
Level 2.