Measurement-computing USB-202-OEM Manuel d'utilisateur télécharger pdf (Page 12)

USB-202-OEM User's Guide Functional Details

Digital I/O

You can connect up to eight digital I/O lines to DIO0 through DIO7. The digital I/O terminals can detect the

state of any TTL-level input. Refer to the schematic shown in Figure 5.

Figure 5. Schematic showing switch detection by digital channel DIO0

If you set the switch to the +5 V input, DIO0 reads TRUE (1). If you move the switch to GND, DIO0 reads

FALSE (0).

Pull-up/down jumper W4

The digital port has 47 kΩ resistors that you can configure as pull-up or pull-down with jumper

W4 (see Figure

2 on page 10 for the location of this jumper).

Unconnected inputs are pulled low by default to 0 V through 47 kΩ resistors. The pull-up/pull-down voltage is

common to all 47 kΩ resistors.

Caution! The discharge of static electricity can damage some electronic components. Before handling the

board, either ground yourself using a wrist strap or touch the computer chassis or other grounded

object to eliminate any stored static charge.

Jumper W4 is configured by default for pull-down; see Figure 6.

Figure 6. Jumper W4 pull-up/down configuration

To pull the digital inputs high (+5V), configure the jumper for pull-up.

Trigger input

The TRIG terminal is an external digital trigger input. The trigger mode is software-selectable for edge- or

level-sensitive.

Counter input

The CTR terminal is a 32-bit event counter that can accept frequency inputs up to 1 MHz. The internal counter

increments when the TTL levels transition from low to high.

Voltage output

The user voltage output (+VO) terminal can output up to 100 mA maximum at approximately +5V. You can use

this terminal to supply power to external devices or circuitry.

Caution! The +VO terminal is an output. Do not connect to an external power supply or you may damage

the device and possibly the computer.

Ground

The analog ground (AGND) terminals provide a common ground for all analog channels. The digital ground

(

GND) terminals provide a common ground for the digital, counter, pacer I/O, and power terminal.

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Measurement-computing USB-202-OEM Manuel d'utilisateur Page 12