External Clock Input/Output - Measurement Computing USB-1208HS-4AO User Manual

USB-1208HS-4AO User's Guide

External clock input/output

Parameter
Terminal names
Terminal types
Terminal descriptions
Input clock rate
Clock pulse width
Input type
Schmitt trigger
hysteresis
Input high voltage
Input low voltage
Output high voltage
Output low voltage
Output current
Counters
Counter terminal names
Counter type
Number of channels
Input type
Schmitt trigger hysteresis
Input high voltage
Input low voltage
Resolution
Maximum input frequency
Counter read/write rates (software paced)
High pulse width
Low pulse width
Table 8. External clock I/O specifications
Specification
AICKI, AICKO, AOCKI, AOCKO
AxCKI: Input, active on rising edge
AxCKO: Output, power on default is 0 V, active on rising edge
AxCKI: Receives sampling clock from external source
AxCKO: Outputs internal sampling clock (D/A or A/D clock) or pulse generated from AxCKI
when in external clock mode
1 MHz maximum.
AxCKI: 400 ns minimum
AxCKO: 400 ns minimum
Schmitt trigger, 33 Ω series resistor, 47 kΩ pull-down to ground
0.4 V to 1.2 V
2.2 V minimum
5.5 V absolute maximum
1.5 V maximum
–0.5 V absolute minimum
0 V recommended minimum
4.4 V minimum (IOH = -50 µA)
3.76 V minimum (IOH = -24 mA)
0.1 V maximum (IOL = 50 µA)
0.44 V maximum (IOL = 24 mA)
±24 mA maximum per terminal (see "Power" section for additional information)
Table 9. Counter specifications
CTR0, CTR1,
Event counter
2
Schmitt trigger, 33 Ω series resistor, 47 kΩ pull-down to ground
0.4 V to 1.2 V
2.2 V minimum
5.5 V absolute maximum
1.5 V maximum
–0.5 V absolute minimum
0 V recommended minimum
32 bits
20 MHz
33 to 8000 reads/writes per second typical, system dependent
25 ns minimum
25 ns minimum
22
Specifications