Measurement Computing USB-2627 - Manual (Page 23)

USB-2627 User's Guide Specifications
23
External trigger
Table 11. External trigger specifications
Parameter Specification
Trigger source TTLTRG
Trigger mode Software programmable for edge or level sensitive, rising or falling edge, high or low
level. Power on default is edge sensitive, rising edge.
Trigger latency 1 µs + 1 clock cycle max
Trigger pulse width 100 ns min
Input type 33 Ω series resistor and 49.9 kΩ pull-down to GND
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
External clock
Table 12. External clock I/O specifications
Parameter Specification
Terminal names XAPCR, XDPCR
Terminal types Input, active on rising edge
Terminal descriptions Receives pacer clock from external source
Input clock rate 1 MHz max
Clock pulse width 100 ns min
Input type 33 Ω series resistor, 47 kΩ pull-down to GND
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
Counter
Table 13. Counter specifications
Parameter Specification
Terminal names CNT0, CNT1, CNT2, CNT3
Number of channels 4 channels
Resolution 32-bit
Counter type Event counter
Input type 33 Ω series resistor, 47 kΩ pull-down to GND
Input source 68-pin SCSI: CNT0 (pin 5), CNT1 (pin 39), CNT2 (pin 4), CNT3 (pin 38)
40-pin (J4): CNT0 (pin 35), CNT1 (pin 34), CNT2 (pin 37), CNT3 (pin 36)
Counter read/writes rates
(software paced) 33 to 8,000 reads/writes per second typ; system dependent
Input high voltage 2.2 V min
Input low voltage 1.5 V max
Maximum input voltage range –5 V to +10 V max
Input frequency 20 MHz, max
High pulse width 100 ns, min
Low pulse width 100 ns, min