DAQ VXI-SC-1000, User Manual

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Chapter 4 Theory of Operation
VXI-SC-1102 User Manual 4-30
©
National Instruments Corporation
The major components of the VXI-SC-1102 are as follows:
• VXIbus interface
• Digital control circuitry
• Analog circuitry
The VXI-SC-1102 consists of 32 multiplexed input channels, each with
a software-programmable gain of 1 or 100. Each input channel has its
own lowpass filter with a cutoff frequency of 2 Hz. The VXI-SC-1102
also has digital control circuitry for automatic control of channel
scanning, temperature sensor selection, and gain selection.
VXIbus Interface
The VXI-DAQ module controls the VXI-SC-1102 over the VXIbus.
The VXI-SC-1000 carrier module serves as an interface from the
VXI-SC-1102 to the VXIbus.
Digital Control Circuitry
The digital control circuitry consists of the address handler and the
following registers: Module ID, Configuration, Status, EEPROM, Gain,
and Channel. The address handler controls which register is being
addressed. The Module ID Register contains the module ID 42 decimal,
a code unique to the VXI-SC-1102. The Configuration Register
configures the VXI-SC-1102 for the desired scanning mode and
connection to the rear signal connector. The Status Register indicates
whether the input channels have settled after a change in the gains. The
EEPROM Register is the address for interfacing with the submodule’s
EEPROM, which contains calibration information. The Gain Register
selects between gains of 1 or 100 for each of the 32 channels. The
Channel Register selects a channel for a single measurement or a start
channel for a scan. Refer to
Software Programming Choices in
Chapter 1, Introduction , of this manual to learn about options for
programming the control circuitry.