Abstract:
An output driver circuit and an input receiver circuit are provided. The output driver circuit employs a series-connected pair of PMOS transistors (102) and coupled to a series-connected pair of NMOS transistors (106, 108). One of the PMOS transistors (102) and one of the NMOS transistors (106) have their gate terminals connected to a pair of power sources (Vref, VCC) such that these transistors maintain a voltage level on the node connecting the transistor to its corresponding pair. The voltage level is maintained during times when the pair of transistors are not conducting current. By maintaining this voltage, the voltage difference between any two terminals of the transistors is held within the maximum allowable voltage of the semiconductor technology. An input receiver circuit is also described which contains an NMOS transistor (120) between the input conductor and receiving inverter circuits. This NMOS transistor (120) has its gate terminal connected to a power supply (VCC) conveying the same voltage as the power supply for the integrated circuit core. The NMOS transistor (120) limits the voltage at the input of the receiving inverter circuits to no more than the power supply voltage (VCC). The circuits may be combined to form an input/output driver circuit.
Abstract:
An integrated circuit is presented having a driver circuit programmable to produce a variety of output voltages and conductive to the voltage levels of circuits interfaced by the integrated circuit. The integrated circuit includes programmable pull up and pull down functions. The integrated circuit may be configured into an application having devices powered by a power supply voltage which is substantially larger than the voltage supplying the core section of the integrated circuit. Additionally, the present integrated circuit may be configured into other applications having devices powered by a power supply voltage substantially similar to the voltage supplying the integrated circuit core section. The present integrated circuit therefore retains utility for a large variety of applications. The pull up and pull down transistors may be programmed to provide a resistive one, resistive zero, or neither.
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. Pullpup 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.
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. Pullpup 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.