Implementation Approaches to Sequencing in Microprocessor-Based Controllers
M. Sreetharan, F. Langenbacher · 1985
Traditional relay-based sequencing is increasingly being replaced by microprocessor-based programmable sequence controllers. Microprocessor-based sequencers are flexible, easy to use and eliminate the expensive reworking of hardwired logic each time a sequencing scheme is revised. However, the logical (bit-oriented) nature of the computations involved in implementing sequencing systems offer considerable challenge to the designers of microprocessor-based (byte/word oriented) sequencers to provide novel software and/or hardware architectures that are cost effective to implement and meet the speed requirements. This paper examines several possible implementation techniques of automatic digital sequencers. In particular, it describes the requirements and the design concepts that formed the basis of the sequencer implemented as part of a multi-processor based full authority controller at the authors’ company, that is capable of controlling a range of turbines in various applications. A comparative study of the performances of several existing sequencing systems is also presented.