Filter
Top Products
Register-Based Programming 41
Appendix B
Appendix B
Register-Based Programming
About This Appendix
This appendix contains the information you can use for register-based
programming of the E1470A Cascade RF Switch module. The contents
include:
• RegisterAddressing.................................41
• RegisterDefinitions..................................44
• RegisterProgrammingExample........................49
Register Addressing
The E1470A Cascade RF Switch is a register-based module that does not
support the VXIbus word serial protocol. When a SCPI command is sent to
the module, 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
multiplexer 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
h
.
The A16 space is further divided so that the modules are addressed only at
locations above 1FC000
h
within A16. Every module is allocated 64 register
addresses (40
h
). The address of a module is determined by its logical
address (set by the address switches on the module) times 64 (40
h
).
In the case of the Cascade RF Switch module, the factory setting is 120
or 78
h
, so the addresses start at 1E00
h
.
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.