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A16 Address Space
Outside the Command
Module
A16 Address Space
Inside the Command
Module or Mainframe
Appendix B
When the E1406 Command Module is not part of your VXIbus system, the
E1468A/E1469A base address is computed as:
A16
= 1FC000
base
16
or (decimal)
A16
= 2,080,768 + (LADDR * 64)
base
where 1FC000
(2,080,768) is the starting location of the register
16
addresses, LADDR is the module's logical address, and 64 is the number
of address bytes per VXI device.
For example, a Relay Matrix Switch module's Status/Control Register has
an offset of 04
. When you write to or read from this register, the offset is
16
added to the base address to form the register address (using a logical
address of 112):
register address = base address + register offset
= 1FC000
+ (112 * 64)
16
= 1FC000
+ 1C00
16
or
= 2,080,768 + (112 * 64) + 4
= 2,080,768 + 7168 + 4 = 2,087,940
When the A16 address space is inside the E1406 Command Module,
the E1468A/E1469A base address is computed as:
1FC000
+ (LADDR
16
16
or (decimal)
2,080,768 + (LADDR * 64)
where 1FC000
(2,080,768) is the starting location of the VXI A16
h
addresses, LADDR is the module's logical address, and 64 is the number
of address bytes per register-based device. The E1468A/E1469A
factory-set logical address is 112. If this address is not changed, the
module will have a base address of:
1FC000
+ (70
* 40
16
16
or (decimal)
2,080,768 + (112 * 64) = 2,080,768 + 7168 = 2,087,936
+ (LADDR
* 64
)
16
16
+ 04
16
16
+ 04
= 1FDC04
16
16
16
* 64
)
16
) = 1FC000
+ 1C00
16
16
Register-Based Programming 71
= 1FDC00
16
16
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