The DS4520 is a 9-bit nonvolatile (NV) I/O expander with 64 bytes of NV user memory controlled by an I 2CTMcompatible serial interface. The DS4520 offers users a digitally programmable alternative to hardware jumpers and mechanical switches that are being used to control digital logic nodes. Furthermore, the digital state of each pin can be read through the serial interface. Each I/O pin is independently configurable. The outputs are open drain with selectable pullups. Each output has the ability to sink up to 12mA. Since the device is NV, it powers up in the desired state allowing it to control digital logic inputs immediately on power-up without having to wait for the host CPU to initiate control.