Agilent Technologies E2259A, User'S Manual And Programming Manual, Page: 36 / 52

Register Descriptions 33
40
h
(64) is the number of address bytes allocated per module
For example, if the M-Module has a logical address of 78
h
(120) the A16
base address becomes:
1FC000
h
+ (78
h
· 40
h
) = 1FC000
h
+ 1E00
h
= 1FDE00
h
or (decimal)
2,080,768 + (120 · 64) = 2,080,768 + 7680 = 2,088,448
A16 Address Space
Outside the Command
Module
When an Agilent E1406 Command Module is not part of your system,
the base address is computed as:
C000
h
+ (LADDR
h
· 40
h
)
or (decimal)
49,152 + (LADDR · 64)
Where:
C000
h
(49,152) is the A16 starting address
LADDR is the module’s logical address
40
h
(64) is the number of address bytes allocated per module
For example, if the M-Module has a logical address of 78
h
(120) the A16
base address becomes:
C000
h
+ (78
h
· 40
h
) = C000
h
+ 1E00
h
= DE00
h
or (decimal)
49,152 + (120 · 64) = 49,152 + 7680 = 56,832
Addressing
A16 Registers
As shown in Figure 3-1, VXI registers for an M-Module are mapped into
A16 address space by the Agilent E2251 Carrier. To access one of these
registers, add the A16 base address to the register offset. For example, an
M-Module’s VXI Status/Control Register has an offset of 04
h
. To access
this register (assuming the system does not have an Agilent E1406
Command Module), use the register address:
1FDE00
h
+ 04
h
= 1FDE04
h
or (decimal)
2,088,488 + 4 = 2,088,452
Addressing
A24 Registers
As shown in Figure 3-1, most of the registers for an M-Module are mapped
into A24 address space. To access one of these registers:
1. Obtain the A24 base address by reading the VXI Offset Register (06
h
)
in A16 memory.
2. Add the A24 base address to the register offset (see Table 3-2).
For example, if the A24 base address is 200100
h
, to access the Output
Register (10
h
):
200100
h
+ 10
h
= 200110
h