Programmable I/O buffer

摘要

A programmable input/output buffer has a first plurality of pull-down transistors connected between a supply voltage and an electrical system conductor on the integrated circuit and a second plurality of pull-down transistors connected between the electrical conductor and the system reference voltage. Reference circuits generate signals to turn on a first number of said first plurality of pull-up transistors and/or a second number of said second plurality of pull-down transistors to provide an input/output buffer impedance matching the impedance of the external transmission line either sending a signal to the programmable input/output buffer or receiving a signal from the programmable input/output buffer.