National Instruments SCXI-1121 - Manual (Page 66)

Chapter 3 Theory of Operation
SCXI-1121 User Manual 3-4 www.natinst.com
SCXIbus Connector Signal Descriptions
Pin Signal Name Description
A1, B1, C1, D1, A2,
D2,A3, B3, C3, D3, A4,
D4, A5, B5, C5, D5, A6, D6 GUARD Guard—Shields and guards the analog bus lines
from noise.
B2 AB0+ Analog Bus 0+ —Positive analog bus 0 line. Used
to multiplex several modules to one analog signal.
C2 AB0– Analog Bus 0– —Negative analog bus 0 line. Used
to multiplex several modules to one analog signal.
C13-C17, A21, B21, C21,
D21 CHSGND Chassis Ground—Digital and analog ground
reference.
C18 RSVD Reserved.
A19 RESET* Reset—When pulled low, reinitializes the module
to its power-up state. Totem pole. Input.
B19 MISO Master-In Slave-Out—Transmits data from the
module to the SCXIbus. Open collector. I/O.
C19 D*/A Data/Address—Indicates to the module whether
address information or data information is being
sent to the module on MOSI. Open collector. I/O.
D19 INTR* Interrupt—Active low. Causes data that is on
MOSI to be written to the Slot-Select Register in
Slot 0. Open collector. Output.
A20, B20, C20, D20 V– Negative Analog Supply— –18.5 to –25 V.
A22, B22, C22, D22 V+ Positive Analog Supply— +18.5 to +25 V.
A23, D23 +5 V +5 VDC Source—Digital power supply.
B23 SPICLK Serial Peripheral Interface (SPI) Clock—Clocks
the serial data on the MOSI and MISO lines. Open
collector. I/O.
C23 MOSI Master-Out Slave-In—Transmits data from the
SCXIbus to the module. Open collector. I/O.