Digital Input / Output; Interrupt Input - Measurement Computing USB-4301 User Manual

USB-4301 User's Guide
Parameter
12 MHz crystal oscillator accuracy
High pulse width (clock input)
Low pulse width (clock input)
Gate width
Input low voltage
Input high voltage
Output low voltage @ IIl=4 mA
Output high voltage @ IIH= 4 mA

Digital input / output

Digital type
Number of I/O
Configuration
Input high voltage
Input low voltage
Output high voltage
Output low voltage
Data transfer
Power-up / reset state
Digital I/O transfer rate
(system paced)
Pull-up/pull-down configuration
Pull-up and pull-down configurations are available using the DI CTL terminal block pin 19. The
Note 1:
pull-down configuration requires the DI CTL pin (pin 19) to be connected to a GND pin (pin 10,
20, 38, or 48). For a pull-up configuration, the DI CTL pin should be connected to a +5V
terminal pin (pin 8 or 18).

Interrupt Input

Implementation
Interrupt characteristics
Firmware routines
Event latency to PC
Maximum event notification rate
Interrupt latency for latch operations
The interrupt rate, when transferring information to the PC (event notification), is limited by the
Note 2:
USB to a theoretical limit of 1kHz. Some systems may not be able to achieve this maximum rate
due to differences in USB controller implementation, traffic on the USB, or operating system
activity.
Conditions
±50 ppm
25 ns min
25 ns min
70 ns min
-0.5 V min, 0.8V max
2.0 V min, USB +5V power max
0.4 V max
2.4 V min
Table 2. Digital I/O specifications
Discrete, 5V/TTL compatible
Output: 74ACT373
Input: 74ACT373
8 input, 8 output
1 bank of 8 as output, 1 bank of 8 as input
2.0 V min,5.5 V absolute max
0.8 V max, –0.5 V absolute min
3.3 volts min @ -24 mA (Vcc = 4.5 V)
0.8 volts max @ 10 mA
Programmed I/O
Digital outputs reset to TTL low
System dependent, 33 to 1000 port reads/writes or single bit reads/writes per
second.
User configurable for pull-up/-down through 47 kΩ resistor (Note 1).
All pins floating (default)
Table 3. Interrupt specifications
Interrupts the microcontroller operation on the device to execute one or more of
several firmware routines.
Rising edge (default) or falling edge triggered, user selectable
Any or all of the following can be activated by the user:
 Generate USB event notification
 Latch digital inputs (Reading digital inputs returns most recently latched
value.)
 Latch digital outputs (Most recently written digital output value is latched.)
 Save counts on any/all of counters 1-5.
1-33 ms (4 ms typical)
33-1000 Hz (system dependent) (Note 2)
100 µs maximum (80 µs typical)
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Specifications