USB-1608GX-2AO User's Guide
Specifications
20
External clock input/output
Table 12. External clock I/O specifications
Parameter
Specification
Terminal names
AICKI, AICKO
AOCKI, AOCKO
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 D/A or A/D sampling clock, or the pulse generated from
AxCKI when in external clock mode.
Input clock rate
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 13. 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
