MC34978AES is a 22-channel multiple-switch detection interface with a programmable wetting current. It is designed to detect the closing and opening of up to 22 switch contacts. The switch status, either open or closed, is transferred to the microprocessor unit (MCU) through a serial peripheral interface (SPI). This SMARTMOS device also features a 24-to-1 analog multiplexer for reading the input channels as analog inputs. The analog selected input signal is buffered and provided on the AMUX output pin for the MCU to read. The application includes heating ventilation and air conditioning (HVAC), lighting, central gateway/in-vehicle networking, gasoline engine management (automotive), programmable logic control (PLC), process control, temperature control, input-output control (I/O Control), single board computer, Ethernet switch (industrial).