National Instruments 653X Manuale Utente

© National Instruments Corporation

When the computer is first turned on, all lines are configured for input and 
in the high-impedance state. By default, the data and control lines in the 
653X device are pulled down, even if the CPULL and DPULL are 
disconnected. You can select the biasing of control and data signals using 
the CPULL and DPULL lines:

•

CPULL line—For control lines, it is a user-configurable 2.2 k

Ω 

internal resistor. You can connect the line to +5 VDC (pull up) or 
connect the line to ground (pull down).

•

DPULL line—For data lines, it is a user-configurable 100 k

Ω internal 

resistor. You can connect the line to +5 VDC (pull up) or connect the 
line to ground (pull down).

Do not connect CPULL, DPULL, or any other line directly to an external power 

supply while the 653X device is powered off. Doing this may prevent your computer from 
booting.

For example, if you are using active-low handshaking signals, you can 
connect the CPULL line to +5 V to place the handshaking lines in the high, 
inactive state at power up.

The +5 V pin on the I/O connector supplies power from the computer 
power supply through a self-resetting fuse. The fuse resets automatically 
within a few seconds after removal of an overcurrent condition. The power 
pin is referenced to the GND pins and can supply power to external digital 
circuitry. The power ratings for the +5 V pin for the various 653X devices 
are shown in Table D-1.

Table D-1.   653X Power Ratings

PCI-DIO-32HS

+4.65 to +5.25 VDC at 1 A

PXI-6533

AT-DIO-32HS

DAQCard-6533 for PCMCIA

+4.65 to +5.25 VDC at 250 mA