Electrical erasure and ISP also mean that production pc boards don't require sockets for chip mounting. Eliminating sockets improves reliability and permits surface mounting. During the crush of prototype checkout, design engineers appreciate being able to immediately update programmable logic without removing ICs from sockets. With all of these benefits, it's a wonder that anyone still designs boards with nonvolatile ICs that require separate programming. Some pointers will help you design boards so that ISP nonvolatile-chips can deliver their full potential.
Many differences exist between the two groups' electronic architecture.
An ISP chip must be programmable with simple digital stimuli while its pins are connected to other devices. You may wonder why all nonvolatile devices aren't programmable on an in-circuit tester after board assembly. Problem areas divide into chip and board factors. One factor is that some chips are not designed for ISP and erasing. Examples of such chips would be those whose logic pins need supervoltages greater than V CC , those whose V CC rises during programming, those that need UV light for erasure, and those that are OTP and can never be erased.