OM-USB-TEMP-AI User's Guide
Specifications
29
Digital input/output
Table 15. Digital input/output specifications
Digital type
5V CMOS
Number of I/O
8 (DIO0 through DIO7)
Configuration
Independently configured for input or output.
Power on reset is input mode.
Pull-up/pull-down
configuration
All pins pulled up to +5 V via 47 K resistors (default). Contact MCC factory for
pull-down to ground (GND) capability.
Digital I/O transfer rate
(software paced)
Digital input – 50 port reads or single bit reads per second typical.
Digital output – 100 port writes or single bit writes per second typical.
Input high voltage
2.0 V minimum, 5.5 V absolute maximum.
Input low voltage
0.8 V maximum, –0.5 V absolute minimum
Output low voltage
(IOL = 2.5 mA max.)
0.7 V maximum
Output high voltage
(IOH = -2.5 mA max.)
3.8 V minimum
Note 19:
All ground pins on the OM-USB-TEMP-AI (pins 9, 19, 22, 27, 30, 33, 36, 39, 49) are common
and are isolated from earth ground. If a connection is made to earth ground when using both
digital I/O and conductive thermocouples, the thermocouples are no longer isolated. In this case,
thermocouples must not be connected to any conductive surfaces that may be referenced to earth
ground.
Counter
Table 16. CTR I/O specifications
Parameter
Conditions
Specification
Pin name
CTR
Number of channels
1
Resolution
32-bits
Counter type
Event counter
Input type
TTL, rising edge triggered
Input source
CTR screw terminal
Counter read
System dependent, 33 to 1000 reads per second.
Counter read/writes rates
(software paced)
Counter write
System dependent, 33 to 1000 reads per second.
Schmidt trigger hysteresis
20 mV to 100 mV
Input leakage current
±1.0 µA typ.
Input frequency
1 MHz max.
High pulse width
500 nS min.
Low pulse width
500 ns min.
Input high voltage
4.0 V min, 5.5 V absolute max
Input low voltage
1.0 V max, –0.5 V absolute min
Note 20:
All ground pins on the OM-USB-TEMP-AI (pins 9, 19, 22, 27, 30, 33, 36, 39, 49) are common
and are isolated from earth ground. If a connection is made to earth ground with both the counter
(CTR) and conductive thermocouples, the thermocouples are no longer isolated. In this case,
thermocouples must not be connected to any conductive surfaces that may be referenced to
earth ground.
