Horology: time measuring systems or devices – Combined with disparate device
Patent
1993-08-04
1995-03-28
Miska, Vit W.
Horology: time measuring systems or devices
Combined with disparate device
368 46, 364569, 395550, G04B 4700, G04C 1100, G06F 900
Patent
active
054023947
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for operating computing units in communication with each other by serial data transfer over a data bus, each computing unit having its own clock generating system and the computing units exchanging timing information via the data bus.
Data processing arrangements with distributed computing nodes or computing units that are connected via a serial data bus are used predominately in industrial and automobile local networks. The computing nodes comprise data processing devices or signal processing devices that are intended for a specific application. Also included is data transfer between control devices, sensors and regulators. Such local networks usually operate under real time conditions, i.e. computer operations and control interventions must be carried out to accompany the process in specific time windows so that the timely availability of data is ensured. The relevant process parameters must thereby be transferred punctually to the individual computing nodes to ensure optimal process operation. For a local network this means that the computer nodes make sufficient processing capacity available.
In data transfer one differentiates in principle between so-called "broadcast" systems and "point-to-point" systems. In "broadcast" systems a node supplies its data to the bus and all other nodes can listen in. In a "point-to-point" connection only two nodes can be connected to one another in a defined manner in each case, one being a called node.
An example of the data processing systems defined above is the Controller Area Network (CAN), which represents a defacto standard protocol. CAN is based on the open system interconnection (OSI) reference model, which is recommended for open systems that can be expanded any time to include further participants or computing nodes. CAN differentiates between various levels, such as the physical level, the transfer level and the object level.
The physical level defines in substance how signals are transferred. Parameters involved are the transfer medium, the signal level and the timing, the transfer rate and the bit representation. The transfer level includes the kern of the CAN protocol. It forms the connecting link between the object level and the physical level and is responsible for bit-timing, defining the object or message frame, transfer acknowledgement, error recognition and error handling and for arbitration, i.e. conflict resolution, when a plurality of computer nodes access the bus simultaneously. Finally, the object level is responsible for filtering objects or messages and for the handling of the objects, which are associated with a higher-ranking applications level. Objects or messages are thereby transmitted in both directions from and to different applications levels via the bus and respective intermediate physical levels, transfer levels and object levels. The physical level and the object level can vary in dependence upon the respective implementation. However, the transfer level is defined by the protocol.
The fundamental concept of CAN is based on the idea of a common virtual data memory for all nodes of a data processing arrangement defined above, the network undertaking through its structure the task of actualising the data of this common virtual memory. According to the protocol the data to be transmitted from a computing node via the network is assembled to form messages or objects which correspond to a data frame. In the data frame various fields are defined which, for example, indicate the start and end of the frame and define the actual data field. Each object that is defined by the data frame includes, after a start-bit of the frame, a header (identifier) that is dominant or recessive and defines the data name and a priority of the object, by means of which access to the bus is determined. The value of the header thus has a determining influence on the collision-free arbitration in the network. This means that there are messages which have priority over other messages. According to the CAN-protocol the header is
REFERENCES:
patent: 4866606 (1989-12-01), Kopetz
patent: 4886981 (1989-12-01), Lentini et al.
patent: 4890222 (1989-12-01), Kirk
patent: 5040158 (1991-08-01), Lee et al.
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