Measurement Computing USB-1808X, User Manual

Page: 22 / 29

USB-1808X User's Guide Specifications
22
Counter
Table 11. Counter specifications
Parameter Specification
Terminal names CTR0, CTR1
Number of channels 2 channels
Resolution 32-bit
Counter type FPGA
Counter input modes Totalize, Pulse width, Period
Input type Schmitt trigger, 33 Ω series resistor, 47 kΩ pull-down to ground
Input source CTR0
CTR1
Scan clock source Internal input scan clock or external input scan clock (ICLKI pin)
Trigger source

ITRIG (see
External trigger
on page 24)

Digital pattern detection (see
Pattern trigger
on page 24)
Counter read clock Internal or external input scan clock up to 200 kHz
Period/pulse width resolution 20 ns, 200 ns, 2 µs or 20 µs; software-selectable
Input high voltage 2.2 V min, 5.5 V max
Input low voltage 1.5 V max, –0.5 V min
Schmitt trigger hysteresis 0.4 V min, 1.2 V max
Input frequency 50 MHz, max
Schmitt trigger hysteresis 0.76 V typ
0.4 V min
1.2 V max
Input high voltage threshold 1.74 V typ
1.3 V min
2.2 V max
Input low voltage threshold 0.98 V typ
0.6 V min
1.5 V max
Input low voltage limit –0.5 V absolute min
0 V recommended min
Quadrature inputs
Table 12. Quadrature input specifications
Parameter Specification
Terminal names ENC0A, ENC0B, ENC0Z; ENC1A, ENC1B, ENC1Z
Number of encoders 2
Signals per encoder A, B and Z
Resolution 20 ns
Maximum frequency 50 MHz
Minimum pulse width 10 ns
De-bounce function None
Scan clock source Internal input scan clock or external input scan clock (ICLKI pin)
Trigger source

ITRIG (see
External trigger
on page 24)

Digital pattern detection (see Pattern trigger on page 24)
Input high voltage 2.2 V min, 5.5 V max
Input low voltage 1.5 V max, –0.5 V min
Absolute maximum input
voltage
5.5 V