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The Base Address
A16 Address Space
Outside the Command
A16 Address Space
Inside the Command
Module or Mainframe
80 Register-Based Programming
When reading or writing to a switch register, a hexadecimal or decimal
register address is specified. This address consists of a base address plus
a register offset. The base address used in register-based programming
depends on whether the A16 address space is outside or inside the E1406
Command Module.
Figure B-1 shows the register address location within A16 as it might be
mapped by an embedded controller. Figure B-2 shows the location of A16
address space in the E1406 Command Module.
When the E1406 Command Module is not part of your VXIbus system (see
Figure B-1), the switch's base address is computed as:
Module
C000
+ (LADDR * 64)
16
where C000
LADDR is the switch's logical address, and 64 is the number of address
bytes per VXI device. For example, the switch's factory-set logical address
is 120 (78
16
address of:
C000
+ (120 * 64)
16
49,152 + (120 * 64) = 49,152 + 7680 = 56,832
When the A16 address space is inside the E1406 Command Module
(see Figure B-2), the switch's base address is computed as:
1FC000
+ (LADDR * 64)
16
where 1FC000
addresses, LADDR is the switch's logical address, and 64 is the number of
address bytes per register-based device. Again, the switch's factory-set
logical address is 120. If this address is not changed, the switch module will
have a base address of:
1FC000
+ (120 * 64)
16
or
2,080,768 + (120 * 64) = 2,080,768 + 7680 = 2,088,448
or 49,152 + (LADDR * 64)
16
(49,152) is the starting location of the register addresses,
16
). If this address is not changed, the switch will have a base
= C000
+ 1E00
16
16
or (decimal)
or
16
(2,080,768) is the starting location of the VXI A16
16
= 1FC000
16
= DE00
16
16
2,080,768 + (LADDR * 64)
+ 1E00
= 1FDE00
16
16
16
Appendix B
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