Measurement Computing USB-DIO24/37 - Manual (Page 12)

12
Chapter 3
Functional Details
Components
The USB-DIO24/37 has the following components, as shown in Figure 5.
 37-pin I/O connector
 USB connector
 LED
Figure 5. USB-DIO24/37 components
37-pin I/O connector
The 37-pin connector provides 24 digital I/O, one counter, six ground, and two 5V power connections.
 The digital I/O is configured as two 8-bit and two 4-bit ports based on the 82C55 specification. Configure
each port independently for input (default) or output.
 The CTR signal is the input to the 32-bit external event counter. The internal counter increments when the
digital input level transitions from low to high, and can count frequencies of up to 1 MHz.
 The six ground (
GND ) connections are identical and provide a common ground for all device functions.
 The two power connections draw power from the USB connector. The +5 pin is a +5 volt output that is
supplied by the computer.
Caution! The +5 V pin is an output. Do not connect to an external power supply or you may damage the
USB-DIO24/37 and possibly the computer