The DS4550 is a 9-bit, nonvolatile (NV) I/O expander with 64 bytes of NV user memory controlled by either an I2CTM-compatible serial interface or an IEEE 1149.1 JTAG port. The DS4550 offers a digitally programmable alternative to hardware jumpers and mechanical switches that are being used to control digital logic nodes. Each I/O pin is independently configurable. The outputs are open drain with selectable pullups. Each output has the ability to sink up to 16mA, and since the device is NV, it powers up in the desired state allowing it to control digital logic inputs immediately on powerup without having to wait for the host CPU to initiate control.