Chapter 4
Theory of Operation
SCXI-1102/B/C User Manual
4-2
©
National Instruments Corporation
The major components of the SCXI-1102/B/C modules are as follows:
•
Rear signal connector
•
SCXIbus connector
•
SCXIbus interface
•
Digital control circuitry
•
Analog circuitry
The SCXI-1102/B/C modules consist of 32 multiplexed input channels,
each with a software-programmable gain of 1 or 100. Each input
channel has its own lowpass filter. The SCXI-1102/B/C modules also
have a digital section for automatic control of channel scanning,
temperature sensor selection, and gain selection.
Rear Signal Connector, SCXIbus Connector, and SCXIbus Interface
The SCXIbus controls the SCXI-1102/B/C module. The SCXIbus
interface connects the rear signal connector to the SCXIbus, allowing a
DAQ device to control the SCXI-1102/B/C module and the rest of the
chassis.
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 a code unique to each type
of SCXI-1102 module:
♦
SCXI-1102—The Module ID is 30 decimal.
♦
SCXI-1102B—The Module ID is 31 decimal.
♦
SCXI-1102C—The Module ID is 62 decimal.
The Configuration Register configures the SCXI-1102/B/C modules 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 module 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
