In electronics, glue logic refers to the custom electronic circuitry needed to ensure compatibility for interfacing off-the-shelf semiconductor components. This is often achieved with the use af a CPLD or FPGA.
It's a simple logic circuit that is used to connect complex logic circuits together. For ex. an ASIC chip may contain large functions, such as a microprocessor and memory which are tied together via small amounts of glue logic
Glue logic is the logic required to interface circuit modules. The modules are typically complex chips such as microcontrollers, RAM, and peripheral ICs (for example, ADCs).