Input Sequencer; External Acquisition Scan Clock - Measurement Computing USB-1616HS-BNC User Manual

USB-1616HS-BNC User's Guide

Input sequencer

Analog, digital, and counter inputs can be scanned based on either an internal programmable timer or an
external clock source.
Input scan clock sources: two (see Note 3)
Programmable parameters per scan
Depth
Onboard channel-to-channel scan rate
External input scan clock (XAPCR)
maximum rate
Clock signal range:
Minimum pulse width
The maximum scan clock rate is the inverse of the minimum scan period. The minimum scan
Note 3:
period is equal to 1 µs times the number of analog channels. If a scan contains only digital
channels, then the minimum scan period is 250 ns.
Some platforms can sustain clock rates up to 83.33 ns.

External acquisition scan clock

Pin name XAPCR
Pin type Bidirectional
Input Maximum rate
 Analog: 990 kHz
 Digital: 4 MHz if no analog channels are enabled, 1 MHz with analog channels enabled
Clock input signal range:
 Logical zero: 0 V to 1.0 V
 Logical one: 2.3 V to 5.0 V
Input pulled up to +3.3 V through 2.47 kΩ
Minimum pulse width: 50 ns high, 50 ns low
Output Clock output signal range:
 Logical one: 137 Ω to +3.3 V
 Logical zero: 130 Ω to ground
Output pulse width: 42 ns high, occurs on every rising edge of the internal pacer clock.
Table 6. Input sequencer specifications
Internal, programmable:
 Analog channels from 1 µs to 1 s in 20.83 ns steps.
 Digital channels and counters from 250 ns to 1 s in 20.83 ns steps.
External. TTL level input (XAPCR):
 Analog channels down to 1 µs minimum
 Digital channels and counters down to 250 ns minimum
Programmable channels (random order), programmable gain
512 locations
Analog: 1 MHz maximum
Digital: 4 MHz if no analog channels are enabled, 1 MHz with analog
channels enabled
Analog: 1.0 MHz
Digital: 4 MHz if no analog channels are enabled, 1 MHz with analog
channels enabled
Logical zero: 0 V to 0.8 V
Logical one: 2.4 V to 5.0 V
50 ns high, 50 ns low
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Specifications