Measurement-computing USB-202 Manuel d'utilisateur télécharger pdf (Page 16)

USB-202 User's Guide Specifications

Digital input/output

Table 8. Digital input specifications

Parameter

Specification

Digital type

TTL

Number of I/O

Configuration

Each bit may be configured as input (power on default) or output

Pull-up configuration

The port has 47 kΩ resistors that may be configured as pull-up or pull-down with an

internal jumper. The factory configuration is pull-down.

Digital I/O transfer rate

(system-paced)

33 to 4000 port reads/writes per second typ, system dependent

Input low voltage threshold

0.8 V max

Input high voltage threshold

2.0 V min

Input voltage limits

5.5 V absolute max

–0.5 V absolute min

0 V recommended min

Output high voltage

4.4 V min (IOH = –50 µA)

3.76 V min (IOH = –24 mA)

Output low voltage

0.1 V max (IOL = 50 µA)

0.44 V max (IOL = 24 mA)

Output current

±24 mA max

External digital trigger

Table 6. External digital trigger specifications

Parameter

Specification

Trigger source

TRIG input

Trigger mode

Software configurable for edge or level sensitive, rising or falling edge, high or low

level. Power on default is edge sensitive, rising edge.

Trigger latency

1 µs + 1 pacer clock cycle max

Trigger pulse width

125 ns min

Input type

Schmitt trigger, 47 kΩ pull-down to ground

Schmitt trigger hysteresis

1.01 V typ

0.6 V min

1.5 V max

Input high voltage threshold

2.43 V typ

1.9 V min

3.1 V max

Input low voltage threshold

1.42 V typ

1.0 V min

2.0 V max

Input voltage limits

5.5 V absolute max

–0.5 V absolute min

0 V recommended min

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Measurement-computing USB-202 Manuel d'utilisateur Page 16

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