Agilent Technologies E8462A, User Manual

Page: 131 / 156

Register-Based Programming 129
Appendix B
Register-Based Programming
About This Appendix
The Agilent E8462A 256-Channel Relay Multiplexer is a register-based
module which does not support the VXIbus word serial protocol. When a
SCPI command is sent to the multiplexer, the instrument driver parses the
command and programs the multiplexer at the register level.
Register-based programming is a series of reads and writes directly to the
multiplexer registers. This increases throughput speed since it eliminates
command parsing and allows the use of an embedded controller. Also,
register programming provides an avenue for users to control a VXI module
with an alternate VXI controller device and eliminates the need for using an
Agilent E1405/E1406 Command Module.
This appendix contains the information you need for register-based
programming. The contents include:
•
Register Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 129
•
Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 133
•
Program Timing and Execution . . . . . . . . . . . . . . . . . . . . . . Page 139
•
Programming Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 141
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) is
allocated a 32 word (64 byte) block of addresses. Figure B-1 shows the
register address location within A16 as it might be mapped by an embedded
controller. Figure B-2 shows the location of A16 address space in the
Agilent E1405B and E1406A Command modules.
The Base Address
When you are reading from, or writing to, a multiplexer register, a
hexadecimal or decimal register address is specified. This address consists
of a base address plus a register offset.
The base address used in register-based programming depends on whether
the A16 address space is outside or inside the Agilent E1406A Command
Module.