Measurement Computing USB-1608G, User Manual

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USB-1608G Series User's Guide Specifications
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External clock input/output
Table 13. External clock I/O specifications
Parameter Specification
Terminal names AICKI, AICKO,
AOCKI, AOCKO (USB-1608GX-2AO only)
Terminal types AxCKI: Input, active on rising edge
AxCKO: Output, power on default is 0 V, active on rising edge
Terminal descriptions AxCKI: Receives sampling clock from external source
AxCKO: Outputs the internal sampling clock (D/A or A/D clock) or the pulse generated
from AxCKI when in external clock mode.
Input clock rate USB-1608G: 250 kHz max
USB-1608GX: 500 kHz max
USB-1608GX-2AO: 500 kHz max
Clock pulse width AxCKI: 400 ns min
AxCKO: 400 ns min
Input type Schmitt trigger, 33 Ω series resistor, 47 kΩ pull-down to ground
Schmitt trigger hysteresis 0.4 V to 1.2 V
Input high voltage 2.2 V min
5.5 V absolute max
Input low voltage 1.5 V 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 = –2.5 mA)
Output low voltage 0.1 V max (IOL = 50 µA)
0.44 V max (IOL = 2.5 mA)
Output current ±2.5 mA max
Counter
Table 14. Counter specifications
Parameter Specification
Terminal names CTR0, CTR1
Number of channels 2 channels
Resolution 32-bit
Counter type Event counter
Input type Schmitt trigger, 33 Ω series resistor, 47 kΩ pull-down to ground
Input source CTR0 (pin 52)
CTR1 (pin 51)
Counter read/writes rates
(software paced) 33 to 8000 reads/writes per second typ, system dependent
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 20 MHz, max
High pulse width 25 ns, min
Low pulse width 25 ns, min