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Using This Appendix
Register Programming vs. SCPI Programming
Register Addressing
Appendix B
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Register-Based Programming
This appendix contains information you can use for register-based
programming of the E1476A 64-Channel, 3-Wire Multiplexer, including:
•
Register Programming vs. SCPI Programming . . . . . . . . . . .101
•
Register Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
•
Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
•
Program Timing and Execution . . . . . . . . . . . . . . . . . . . . . . .108
•
Programming Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
The E1476A 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 resident in the E1406 Command Module parses the
command and programs the multiplexer at the register level.
NOTE
If SCPI is used to control this module, register programming is not
recommended. The SCPI Driver maintains an image of the card state.
The driver will be unaware of changes to the card state if you alter the
card state by using register writes.
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 eliminate the need for using an
E1406 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 eight registers, the E1476A
multiplexer uses eight of the 64 addresses allocated. Figure B-1 shows the
register address location within A16as it might be mapped by an embedded
controller. Figure B-2 shows the location of A16 address space in the E1406
Command Module.
Appendix B
Register-Based Programming 101
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