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External trigger, External clock input/output – Measurement Computing USB-1408FS User Manual

Page 23

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USB-1408FS User's Guide

Specifications

23

External trigger

Table 10. External digital trigger specifications

Parameter

Conditions

Specification

Trigger source

External, digital

TRIG_IN

Trigger mode

Software-selectable

Edge sensitive: user configurable for CMOS compatible rising or
falling edge

Trigger latency

10 µs max

Trigger pulse width

1 µs 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
3.1V max

Input high voltage limit

5.5 V absolute max

Input low voltage
threshold

1.42 V typ
1.0 V min
2.0 V max

Input low voltage limit

-0.5 V absolute min
0 V recommended min

External clock input/output

Table 11. External clock I/O specifications

Parameter

Conditions

Specification

Pin name

SYNC

Pin type

Bidirectional

Direction
(software-selectable)

Output

Outputs internal A/D pacer clock. Active on rising edge.

Input (default)

Receives A/D pacer clock from external source. Active on rising edge.

Input clock rate

48 kHz, maximum

Clock pulse width

Input mode

1 µs min

Output mode

5 µs 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
3.1V max

Input high voltage limit

5.5 V absolute max

Input low voltage
threshold

1.42 V typ
1.0 V min
2.0 V max

Input low voltage limit

-0.5 V absolute min
0 V recommended min

Output high voltage

4.4 V min (IOH = –50 µA)
3.80 V min (IOH = –8 mA)

Output low voltage

0.1 V max (IOL = 50 µA)
0.44 V max (IOL = 8 mA)