Theory of Operation Chapter 3
SCXI-1120 User Manual 3-4 © National Instruments Corporation
SCXIbus Connector Signal Descriptions
Pin Signal Name Description
A1, B1, C1, D1, GUARD Guard – Shields and guards the analog bus lines
A2, D2, A3, B3, from noise.
C3, D3, A4, D4,
A5, B5, C5, D5,
A6, D6
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, CHSGND Chassis Ground – Digital and analog ground
B21, C21, D21 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
Slot 0. Open collector. Output.
A20, B20, C20, V- Negative Analog Supply – -18.5 V to -25 V.
D20
A22, B22, C22, V+ Positive Analog Supply – +18.5 V to +25 V.
D22
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.