User manual

Register-Based Programming 99Appendix B
Appendix B
Register-Based Programming
About This Appendix
This appendix contains information for register-based programming of the
E1460A Relay Multiplexer module, including:
• Register Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
• Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
• Programming Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
Register Addressing
The E1460A Relay Multiplexer module is a register-based module that does
not support the VXIbus word serial protocol. When a SCPI command is sent
to the multiplexer, the E1406A Command
Module 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, if
slot 0, the resource manager, and the computer (GPIB) interface are
provided by other devices, a C-Size system can be downsized by removing
the command module.
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. With twelve registers, the E1460A
multiplexer uses twelve of the 64 addresses allocated.
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 E1406A command module.
The Base Address When you are reading 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 command module.