TTL input except for D13-D15, which are Schmitt trigger input. Each D pin has a 10 M
Ω
resistor
connected to ground.
DB25 Pinouts:
1: D0
6: D5
11: +5V
16: GND
21: D11
2: D1
7: D6
12: +5V
17: GND
22: D12
3: D2
8: D7
13: +5V
18: D8
23: D13
4: D3
9: NC
14: GND
19: D9
24: D14
5: D4
10: +5V
15: GND
20: D10
25: D15
These digital I/O can detect the state of a switch using the same circuit shown in Figure 2-5.
Because the D pins have no overvoltage/short-circuit protection, the user must be
careful to avoid damage. The following are examples of things that could damage a D
pin and/or the entire LabJack:
•
Shorting a high output to ground (or any potential other than +5V).
•
Shorting a low output to a nonzero voltage (such as +5V).
•
Exceeding the voltage limits specified in Appendix A.
Software
The functions AOUpdate or DigitalIO are used to set the direction, set the state, and/or read the
state, of each D pin. In addition, DigitalIO also returns the current state of the direction and
output registers. Both of these functions take up to 20 ms to execute, providing a maximum
update rate of at least 50 Hz per pin.
2.5 CNT
The input connection to the 32-bit counter is made at screw-terminal CNT. This input has a
Schmitt Trigger buffer, and the counter is incremented each time the voltage at CNT changes
from less than 1 volt to greater than 4 volts. Frequencies up to at least 1 MHz can be counted.
Software
The functions AOUpdate or Counter are used to reset or read the counter. If a reset is
specified, the counter is read first. Both of these functions take up to 20 ms to execute,
providing a maximum update rate of at least 50 Hz.
2.3 CAL – STB
These terminals are used during testing and calibration. The CAL terminal is a pre2.5
volt source and can be used to provide a few milliamps.
2.4 +5V
The LabJack has a n5 volt internal power supply. Power can be drawn from this power
supply by connecting to the +5V screw-terminals, or the +5V pins on the DB25 connector. The
total amount of current that can be drawn from the +5V pins, analog outputs, and digital outputs,
is 450 mA for most desktop computers and self-powered USB hubs. Some notebook
computers and bus-powered hubs will limit this available current to about 50 mA.
2.5 GND
The GND connections available at the screw-terminals and DB25 connector provide a common
ground for all LabJack functions.