Device and method for programming high impedance states upon select

Abstract

An integrated circuit incorporating programmable pullup and pulldown devices into each input/output (I/O) pad is described. Each I/O pad may be individually programmed to include a pullup or pulldown function. Pullup and pulldown resistors may be removed from a system employing the present integrated circuit. Programming of the I/O pads may be accomplished in a number of ways. Following the deassertion of a reset signal, high impedance states may be transferred into a shift data storage within the integrated circuit. Once the states are received, they are shifted to the respective I/O pads through a serial chain connection of the pullup and pulldown devices within each I/O pad. The states are then maintained by each pullup and pulldown device until a subsequent reprogramming. Software programs may also reprogram the pullup and pulldown states by storing appropriate values into the shift data storage. The program then sets an appropriate value into a status register included within the integrated circuit. Upon detection of the value within the status register, the integrated circuit reprograms the high impedance states of the I/O pads with the states stored in the shift data storage.