Chapter 2 Configuration and Installation
© National Instruments Corporation 2-41 SCXI-1121 User Manual
The digital timing signals are pins 36 and 43.
• Pin 36 is used as a clock by the SCXI-1121 to increment the
MUXCOUNTER after each conversion by the data acquisition board
during scanning. This signal is referred to as SCANCLK. See
Chapter3, Theory of Operation, for a description of MUXCOUNTER.
• Pin 43 is a reserved digital input.
The following specifications and ratings apply to the digital I/O lines.
Absolute maximum voltage
Input rating 5.5 V with respect to DIG GND
Digital input specifications (referenced to DIG GND):
VIH input logic high voltage 2 V minimum
VIL input logic low voltage 0.8 V maximum
II input current leakage ±1 µA maximum
Digital output specifications (referenced to DIG GND):
VOH output logic high voltage 3.7 V minimum at 4 mA maximum
VOL output logic low voltage 0.4 V maximum at 4 mA maximum
Table 2-16. SCXIbus to SCXI-1121 Rear Signal Connector to Data Acquisition Board Pin Equivalences
SCXIbus Line
SCXI-1121
Rear Signal
Connector MIO-16 Lab-NB/Lab-PC
Lab-PC+/Lab-LC PC-LPM-16
MOSI SERDATIN ADIO0 PB4 DOUT4
D*/A DAQD*/A ADIO1 PB5 DOUT5
INTR* SLOT0SEL* ADIO2 PB6 DOUT6
SPICLK SERCLK EXTSTROBE* PB7 DOUT7
MISO SERDATOUT BDIO0 PC1 DIN6