This paper describes new fault-tolerant technology using a simple object-based Autonomous Decentralized System (ADS) model. Recent advances in processor technology have made it possible to connect not only computers but also devices to networks resulting in an increasing number of nodes in a system. Control logic of a computer or a controller has become widely distributed among a huge number of devices, such as sensors and actuators. More flexible and lower cost systems are required because of the downsizing of control systems. In order to achieve these requirements, the Structured Autonomous Control Processor (SACP) model and a message selection method has been proposed. This model and method show how scalable fault-tolerance and increased maintainability of device-level distributed computing systems can be achieved. SACP and the message selection method are applied to a SACP chip and the effectiveness has been verified. Some SACP functions have become the defacto standard for communication protocol used in manufacturing systems and have started to be used wide world.