Agilent Technologies E1470A user manual Appendix B, About This Appendix, Register Addressing

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:

• Register Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

• Register Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

• Register Programming Example. . . . . . . . . . . . . . . . . . . . . . . .49

Register Addressing

Addressing Overview

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.

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 1F0000h.

The A16 space is further divided so that the modules are addressed only at locations above 1FC000h within A16. Every module is allocated 64 register addresses (40h). The address of a module is determined by its logical address (set by the address switches on the module) times 64 (40h).

In the case of the Cascade RF Switch module, the factory setting is 120 or 78h, so the addresses start at 1E00h.

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.

Appendix B Register-Based Programming 41