National Instruments 653 Series User Manual page 109

Power-On State
Caution Do not connect CPULL, DPULL, or any other line directly to an external power
supply while the NI 653X is powered off. This action may prevent your computer from
booting.
Power Connections
© National Instruments Corporation
When the computer is first powered on, all lines are configured for input
and are in the high-impedance state. By default, the data and control lines
in the NI 653X 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 kΩ
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 kΩ internal
resistor. You can connect the line to +5 VDC (pull up) or connect the
line to ground (pull down).
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
NI 653X devices are shown in Table D-1.
Table D-1. NI 653X Power Ratings
Device
NI PCI-DIO-32HS
NI PXI-6533
NI AT-DIO-32HS
NI DAQCard-6533 for PCMCIA
Appendix D
+4.65 to +5.25 VDC at 1 A
+4.65 to +5.25 VDC at 250 mA
D-5
Hardware Considerations
Power Rating
NI 653X User Manual