An ASIC is custom made for an intended application or group of applications of one company. An ASSP is an ASIC but for multiple companies. Let’s take the automotive industry as an example. More and more chips are embedded in a car. Usually, the car constructors buy systems from their vendors. These systems consist of many chips and cables to connect them. If I oversimplify, one chip has a fail rate of one in 1 million and 20.000 chips in a car then one in 50 cars would have a defected chip when delivered. Of course the real calculations are complex based on lifetime tests, complexity of the chip, … . But you get the picture. Hence H-bridge drivers (stepper motor drivers) are being integrated with other functionality, like a microprocessor and maybe LIN and CAN communication, I2C, … . To reduce the number of chips, an ASSP could be a solution to group several seperate IC’s into one.