Chapter 2 Hardware Installation and Configuration
© National Instruments Corporation
2-5
AT-FBUS for Windows NT
Selecting the Memory Base Address
The AT-FBUS board is a memory-mapped device, which means that the
driver software can use the AT-FBUS memory registers as if they were
standard memory. The memory base address of the AT-FBUS is the first
position in the total memory address space occupied by the AT-FBUS.
The AT-FBUS is configured to use memory base address D0000 hex by
default. With this setting, the board uses the memory space from D0000
hex through D4000 hex. If this address range is already used by another
device, or if you are installing more than one board, complete the
following steps to reconfigure the memory base address setting. If you
are installing more than one AT-FBUS board, each board must use a
unique memory base address. Your computer’s conventional DRAM and
all other devices cannot use the memory space you assign to the
AT-FBUS board.
1.
Choose a new memory base address.
You can configure the AT-FBUS to use lower or upper memory.
Lower memory is the memory residing in the first megabyte of
address space. Upper memory is any memory that resides above the
first megabyte. Because the AT bus can only access the first 16 MB
of address space, and the AT-FBUS must have a unique base address
in memory, you must have 8 MB or less of DRAM in your machine
to place the AT-FBUS in upper memory. If these conditions are met,
you must locate the AT-FBUS above your conventional memory and
below the 16 MB upper limit for addresses.
Table 2-2 lists the possible switch settings, the corresponding
memory base address, and the memory space used for each setting.
Bold italic denotes the default setting.
Table 2-2. Memory Base Address Switch Settings
Switch Setting
SW1 SW2 SW3 SW4 SW5 SW6
Base Address
ON
ON
OFF
ON
ON
OFF
0C0000
ON
ON
OFF
ON
OFF
OFF
0C4000
ON
ON
OFF
OFF
ON
OFF
0C8000
ON
ON
OFF
OFF
OFF
OFF
0CC000
ON
ON
ON
ON
ON
OFF
0D0000
ON
ON
ON
ON
OFF
OFF
0D4000
