Agilent Technologies E1468A, User Manual

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Register-Based Programming 69
Appendix B
Appendix B
Register-Based Programming
About This Appendix
This appendix contains the information you can use for register-based
programming of the E1468A/E1469A Relay Matrix Switch modules.
The contents include:
•
Register Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
•
Reading the Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
•
Writing to the Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Register Addressing
The E1468A/E1469A Relay Matrix Switch modules are register-based
modules that do not support the VXIbus word serial protocol. When a
SCPI command is sent to the modules, the instrument driver resident in
the command module parses the command and programs the module at
the register level.
Addressing
Overview
Register-based programming is a series of reads and writes directly to the
module registers. This can increase throughput speed since it eliminates
command parsing and allows the use of an embedded controller. It also
allows use of an alternate VXI controller, eliminating the command module.
To access a specific register for either read or write operations, the address
of the register must be used. Register addresses for the plug-in modules are
in an address space known as VXI A16. The exact location of A16 within a
VXIbus master’s memory map depends on the design of the VXIbus master
you are using. For the E1406 Command Module, the A16 space location
starts at 1F0000
16
.
The A16 space is further divided so that the modules are addressed only at
locations above 1FC000
16
within A16. Every module is allocated 64 register
addresses (40
16
). The address of a module is determined by its logical
address (set by the address switches on the module) times 64 (40
16
).
For the E1468A/E1469A modules, the factory setting is 112 (70
16)
, so the
addresses start at 1C00
16
.
Register addresses for register-based devices are located in the upper 25%
of VXI A16 address space. Every VXI device (up to 256) is allocated a 64
byte block of addresses. Figure B-1 shows the register address location
within A16. Figure B-2 shows the location of A16 address space in the
E1406 Command Module.