Shortcomings of Mini-MAP in high speed real time local area networks

One of the early computer integrated manufacturing (CIM) standards is the manufacturing automation protocol (MAP), developed by General Motors. It has been used satisfactorily at the plant level of the hierarchy, yet its performance does not always satisfy the requirements at other levels of the communication hierarchy. Basically this is due to the complex structure of the protocol. Consequently, a streamlined version of MAP, known as enhanced performance architecture (EPA) or Mini-MAP, was developed. Mini-MAP gives the required performance at cell level and uses a MAP/EPA bridge (node) to communicate with the plant level. Efforts to apply Mini-MAP to fieldbus have been made by allowing for the inclusion of passive nodes on the network. Their function is to control plant elements such as switches, actuators etc. Passive nodes cannot, by themselves, acquire use of the network; they respond only to polling by active nodes. The paper examines the shortcomings of Mini-MAP when applied to the field-bus level