Chapter 4
Register Descriptions
© National Instruments Corporation
4-17
VME-MXI-2 User Manual
Extender A32 Window Register (VWR3)
VMEbus A16 Offset:
10 (hex)
Attributes:
Read/Write
16, 8-bit accessible
15
14
13
12
11
10
9
8
0
A32EN
A32DIR
1
1
A32SIZE[2]
A32SIZE[1]
A32SIZE[0]
7
6
5
4
3
2
1
0
A32BASE[7]
A32BASE[6]
A32BASE[5]
A32BASE[4]
A32BASE[3]
A32BASE[2]
A32BASE[1]
A32BASE[0]
You can use this register to control the mapping of VMEbus A32 space between the
VMEbus and the MXIbus. When programming this register, you do not need to consider
any VMEbus A32 space that the VME-MXI-2 itself requires. This is because the
A24/A32 Base Address Decoder has a higher priority than VWR3, and the VME-MXI-2
will respond to its A32 accesses from both the VMEbus and the MXIbus. This register
conforms to the VXIbus Mainframe Extender specification.
This register takes on a different form when the CMODE bit in the VME-MXI-2 Control
Register (VMCR) is set. This different form does not comply with the VXIbus
Mainframe Extender specification, and the CMODE bit should not be set when using a
VXIbus multiframe Resource Manager. For more information on the CMODE bit, refer
to the VMCR register description.
To accommodate 8-bit masters that write to this register, the window is not enabled until
the lower byte of the register is written. Therefore, 8-bit masters should write the upper
byte first, followed by the lower byte.
Bit
Mnemonic
Description
15
0
Reserved
This bit is reserved and returns 0 when read. This
bit can be written with any value.
14
A32EN
Extender A32 Window Enable
Writing a 1 to this bit enables mapping of
VMEbus A32 space through the Extender A32
Window. When this bit is cleared, no VMEbus
A32 accesses are mapped between the VMEbus
and the MXIbus. This bit is cleared by a hard
reset and is not affected by a soft reset.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
