User manual

Chapter 5 Register Descriptions
© National Instruments Corporation 5-15 VXI-MXI-2 User Manual
13 A16DIR Extender A16 Window Direction
When this bit is set, the address range defined by
A16SIZE[2:0] and A16BASE[7:0] applies to
MXIbus cycles that are mapped in to VXIbus
cycles (inward cycles). When this bit is cleared,
the range applies to VXIbus cycles that are
mapped out to MXIbus cycles (outward cycles).
The complement of the defined range is mapped
in the opposite direction. This bit is cleared by a
hard reset and is not affected by a soft reset.
12-11 1 Reserved
These bits are reserved. They return 11 (binary)
when the VWR1 is read. These bits can be
written with any value.
10-8 A16SIZE[2:0] Extender A16 Window Size
These bits define the size of the range of A16
addresses that map through the Extender A16
Window. They specify the number of address
lines that are compared to the A16BASE[7:0]
bits when determining if a VMEbus A16 access
is in the mapped range. The A16SIZE[2:0] most
significant bits of A16BASE[7:0] are compared,
while the remaining bits are ignored. Thus, the
number of A16 addresses in the range mapped is
256 * 2
8-A16SIZE[2:0]
. These bits are cleared by a
hard reset and are not affected by a soft reset.
7-0 A16BASE[7:0] Extender A16 Window Base
These bits define the base address of the range of
A16 addresses that map through the Extender
A16 Window. They correspond to address lines
15 through 8 (the eight most significant address
lines used in VMEbus A16 space). No part of the
upper one quarter of A16 space will be mapped
through the Extender A16 Window regardless of
the size and base programmed. These bits are
cleared by a hard reset and are not affected by a
soft reset.