Power Connections; Digital I/O Power-Up State Selection; High Dio Power-Up State - National Instruments PC-DIO-96/PnP User Manual

Power Connections

Warning: Under no circumstances should these +5 V power pins be connected

Digital I/O Power-up State Selection

High DIO Power-up State

© National Instruments Corporation
Pins 49 and 99 of the I/O connector are connected to the +5 V supply
from the PC power supply. These pins are referenced to GND and can
be used to power external digital circuitry. This +5 V supply has a 1 A
protection fuse in series. This fuse is self-resetting. Simply remove the
circuit causing the heavy current load and the fuse will reset itself. For
more information on these output pins, see Output Signals in
Appendix A, Specifications.
Power rating
directly to ground or to any other voltage source on the PC-DIO-96/PnP or
any other device. Doing so may damage the PC-DIO-96/PnP and the PC.
National Instruments is
connection.
You may want to power up the PC-DIO-96/PnP's digital I/O lines in a
user-defined state. The PC-DIO-96/PnP facilitates user-configurable
pull-up or pull-down. Each DIO channel is connected to a 100 kΩ
resistor and can be pulled high or low using jumper W1. You can use
W1 to pull all 96 DIO lines high or low. However, if all lines are high,
you may want to pull some lines low. To do this properly, you must
understand the nature of the drive current on those lines and adhere to
TTL logic levels.
If you select the pulled-high mode, each DIO line will be pulled to VCC
(+5 VDC) with a 100 kΩ resistor. If you want to pull a specific line low,
connect between that line and ground a pull-down resistor (R
value will give you a maximum of 0.4 VDC. The DIO lines provide a
maximum of 2.5 mA at 3.7 V in the high state. Use the largest possible
resistor so that you do not use more current than necessary to perform
the pull-down task.
Also, make sure the resistor's value is not so large that leakage current
from the DIO line along with the current from the 100 kΩ pull-up
resistor drives the voltage at the resistor above a TTL low level of
0.4 VDC.
0.5 A per pin at +5 V ±10%
liable for damage resulting from such a
NOT
3-9
Chapter 3 Signal Connections
) whose
L
PC-DIO-96/PnP User Manual