A New Time Independent Asynchronous Protocol and Its Applications

P. Radcliffe, Xinghuo Yu
2007 IEEE Transactions on Industrial Informatics  
Communications both to and between low end microprocessors represents a real cost in a number of industrial and consumer products. This thesis starts by examining the properties of protocols that help to minimize these expenses and comes to the conclusion that the derived set of properties define a new category of communications protocol : Time Independent Asynchronous ( TIA) communications. To show the utility of the TIA category we develop a novel TIA protocol that uses only 2-wires and
more » ... l IO pins on each host. The protocol is analyzed using the Petri net based STG ( Signal Transition Graph) which is widely use to model asynchronous logic. It is shown that STGs do not accurately model the behavior of software driven systems and so a modified form called STG-FT ( STG For Threads) is developed to better model software systems. A simulator is created to take an STG-FT model and perform a full reachability tree analysis to prove correctness and analyze livelock and deadlock properties. The simulator can also examine the full reachability tree for every possible system state ( the cross product of all sub-system states), and analyze deadlock and livelock issues related to unexpected inputs and unusual situations. Reachability pruning algorithms are developed which decrease the search tree by a factor of approximately 250 million. The 2-wire protocol is implemented between a PC and an Atmel Tiny26 microprocessor, there is also a variant that works between microprocessors. Testing verifies the simulation results including an avoidable livelock condition with data throughput peaking at a useful 50 kilobits/second in both directions. The first practical application of 2-wire TIA is part of a novel debugger for the Atmel Tiny26 microprocessor. The approach can be extended to any microprocessor with general IO pins. TIA communications, developed in this thesis, is a serious contender whenever low end microprocessors must communicate with other processors. Consumer and industrial products may be able to achieve cost saving by using this new protocol.
doi:10.1109/tii.2007.898439 fatcat:i6eokjw4zzbqbexvcn2j5e33kq