Measurement Computing USB-DIO24/37 - Manual (Page 15)

15
Chapter 4
Specifications
Typical for 25 °C unless otherwise specified.
Specifications in italic text are guaranteed by design.
Digital input/output
Table 1. Digital I/O specifications
Digital type 82C55
Number of I/O 24 (Port A Bit 0 through Port C Bit7)
Configuration 2 banks of 8 and 2 banks of 4, or
3 banks of 8
Pull up/pull-down configuration All pins pulled up to Vs via 47K resistors (default). Selection available for
pull down to ground. Hardware selectable via zero ohm resistor.
Input high voltage 2.0 V min, 5.5 V absolute max
Input low voltage 0.8 V max, –0.5 V absolute min
Output high voltage (IOH = -2.5 mA) 3.0 V min
Output low voltage (IOH = -2.5 mA) 0.4V max
Power up / reset state Input mode
Counter
Table 2. Counter specifications
Pin name (Note 1) CTR
Counter type Event counter
Number of channels 1
Input type TTL, rising edge triggered
Input source CTR screw terminal
Resolution 32 bits
Schmidt trigger hysteresis 20 mV to 100 mV
Input leakage current ±1 µA
Maximum input frequency 1 MHz
High pulse width 500 ns min
Low pulse width 500 ns min
Input low voltage 0 V min, 1.0 V max
Input high voltage 4.0 V min, 15.0 V max
Note 1: CTR is a Schmitt trigger input