Implementation of firmware on SPC switching systems

The recent trend toward distributed processing in stored-program-controlled (SPC) switching systems has resulted in increased use of firmware. The impact of firmware on SPC switching system reliability and maintainability, after sale of the product to user companies, can be substantial. The author examines both life cycle practices for firmware and the impact of firmware on switching systems, and he suggests means to lessen this impact. He examines present firmware technologies, which indicate a trend toward electrically erasable/programmable firmware devices; shows the importance of parallel development methodologies for firmware and software; shows the advantages of loose coupling between firmware and software; shows a relationship between the quality of firmware product and the quality of service a telephone company provides; and suggest a classification of firmware devices