Guide to In-System Programming (ISP) In-system programming is the ability of some microcontrollers, programmable logic and memory devicesto be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to fitting The primary advantage of this feature is that it allows board manufacturers to integrate programming and testing into a single production phase, rather than requiring a separate programming stage prior to assembly. Typically, devices supporting ISP have internal circuitry to generate any necessary programming voltage from the system's normal supply voltage, and communicate with the programmer via a serial protocol. Most programmable logic devices use a variant of the JTAG protocol for ISP, in order to facilitate easier integration with automated testing procedures. Other devices usually use proprietary protocols or protocols defined by older standards.