Dual Function I/O Port
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-06
By using one input/output (I/O) port for two functions, other I/O ports may be freed up for other uses. An input port is used at the beginning of a program to determine in what operating mode the code should be. At a later time, the same port may be used as an output to indicate successful task completion. The input signal is buffered by an open collector device and the signal's polarity is chosen such that the buffer output will be high when the microcomputer uses the I/O port for an output. Since the buffer's output transistor is off, the I/O port can be toggled as desired. This can help to conserve the I/O ports in a design and minimize additional parts.