National Instruments 653X - Manual (Page 109)

Appendix D Hardware Considerations
© National Instruments Corporation D-5 653X User Manual
Power-On State
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).
Caution 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.
Power Connections
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
Device Power Rating
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