Totem pole output GPIO provide active source and sink current sources and do not rely on a pull up resistor to provide the source current. The four sets of registers within totem pole outputs devices are programmable and provide for: Configuration (Input or Output) control, Input (value), Output (value) or Polarity (active high or low). The PCA9554/54A/55 devices have interrupt outputs and the 8 or 16 I/O pins can be configured for interrupt inputs. These devices have the same I²C address and footprint as the PCF8574/74A/75 but require some software modifications due to the different I/O registers. The PCA9554 and PCA9555 have the same I²C address while the PCA9554A has a slightly different fixed address, allowing 16 devices (eight PCA9554A and eight PCA9554/55 in any combination) to be on the same I²C/SMBus. The PCA9557 features a Hardware Reset pin instead of the interrupt output that allows the device to be reset remotely should the I²C bus hang up. The PCA9557 has the same electrical characteristics as the PCA9554/54A.