Agilent Technologies E1406A, User'S Manual And Scpi Programming Manual

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Register Addressing
Register addresses for register-based devices are located in the upper 25%
of VXI A16 address space. Every VXI device (up to 256 devices per
Command Module) is allocated a 64 byte block of addresses. A device may
or may not use the entire block of addresses. Figure C-1 shows the location
of A16 address space in the Agilent E1406A Command Module.
The Base Address
When you are reading or writing to a device register, a hexadecimal or
decimal register address is specified. This address consists of a base
address plus a register offset.
Determining the
Base Address
The base address of a device in A16 address space is computed as:
1FC000
16
+ (LADDR * 64)
16
or
2,080,768
10
+ (LADDR * 64)
10
where 1FC000
16
(2,080,768
10
) is the starting location of the VXI A16
addresses, LADDR is the device’s logical address, and 64 is the number of
address bytes per register-based device. For example, the Agilent E1411B
multimeter has a factory set logical address of 24. If this address is not
changed, the multimeter will have a base address of:
1FC000
16
+ (24 * 64)
16
1FC000
16
+ 600
16
= 1FC600
16
or
2,080,768
10
+ (24 * 64)
10
2,080,768
10
+ 1536
10
= 2,082,304
10
Register Offset
The register offset is the register’s location in the block of 64 address bytes.
For example, the Agilent E1411B multimeter’s Command Register has an
offset of 08
16
. When you write a command to this register, the offset is
added to the base address to form the register address:
1FC600
16
+ 08
16
= 1FC608
16
or
2,082,304
10
+ 8
10
= 2,082,312
10
260 Agilent E1406A Command Module A16 Address Space Appendix C