The CDP68HC68P1 is a serially addressed 8-bit Input/Output port that allows byte or individual bit control. It consists of three registers, an output buffer and control logic. Data is shifted in and out of the device via shift register that utilizes the SPI (Serial Peripheral Interface) bus. The I/O port data flow is controlled by the Data Direction Register and data is stored in the Data Register that outputs or senses the logic levels at the buffered I/O pins. All inputs, including the serial interface are Schmitt triggered. This device also features a compare function that compares the data register and port pin values for 4 programmable conditions and sets a software accessible flag if the condition is satisfied. The user also has the option of bit-set or bit-clear when writing to the data register.