Patent
1995-09-25
1998-05-05
Auve, Glenn A.
G06F 1300
Patent
active
057489238
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a method for the cyclic transmission of data between at least two control devices with distributed operation, the at least two control devices being interconnected via a serial bus, in particular a CAN bus, and having at least one serial interface and an arithmetic/control unit, data being provided cyclically by the arithmetic/control unit of one of the at least two control devices and being transmitted with the aid of a message via the serial bus and a transmission job for transmitting the message being provided at the serial interface by the arithmetic/control unit of the control device transmitting the message, which job is subsequently handled by the serial interface.
A method for the cyclic transmission of data between at least two control devices with distributed operation is already disclosed in the article "Bussystem fur Kfz-Steuergerate (Bus system for motor vehicle control devices) by W. Botzenhardt, M. Litschel and J. Unruh, VDI Berichte No. 612, pages 459 to 470, 1986. In this article, as an example, the engine speed of an internal combustion engine is determined by an engine controller and cyclically transmitted via a CAN bus system to a transmission controller and a driver information system. The engine speed of the internal combustion engine is subject to continuous variation in the running mode of the internal combustion engine. Therefore, it has to be cyclically transmitted at short time intervals from the engine control device to the transmission controller and to the drive information system. The transmission of the speed data takes place with the aid of a message containing the speed data. The CPU of the engine control device cyclically calculates the engine speed data from the measurement signal of the connected speed sensor. It then passes to the CAN interface of the control device a transmission request for the speed data. In the process, it stores the data to be transmitted in a memory of the CAN interface and sets a transmission request bit in a status register of the CAN interface. However, in the most unfavorable case, a relatively large time difference can occur between the transmission request and the actual transmission of the speed data.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved method of cyclic transmission of data between at least two control devices with distributed operation of the above-described type in which the effects of the above-described disadvantages are reduced in comparison to current methods.
It is also an object of the present invention to provide a bus subscriber station for use in the control devices used in performing the method according to the invention.
According to the invention, the method for cyclic transmission of data between at least two control devices with distributed operation, wherein the at least two control devices are interconnected via a serial bus and each include at least one serial interface and an arithmetic/control unit, and the data is provided cyclically by the arithmetic/control unit of one of the at least two control devices, includes the steps of: message including the data in the serial interface of the control device transmitting the data; control devices transmitting the message at a predetermined instant or time by means of the arithmetic/control unit of the control device transmitting the message; message and cyclically or periodically replacing the data in the message with the updated data after the feeding of the transmission job to the serial interface and prior to transmission of the message via the serial bus; and devices by means of the serial interface of the control device transmitting the message after step c).
In contrast, the method according to the invention has the advantage that the transmitted data is considerably more contemporaneous than that of the prior art methods.
A further advantage is that the reduction in the loss of contemporaneity does not necessitate any interventions in the transmission protoco
REFERENCES:
patent: 5345384 (1994-09-01), Przybyla et al.
patent: 5402394 (1995-03-01), Turski
patent: 5446846 (1995-08-01), Lennartsson
patent: 5483230 (1996-01-01), Mueller
patent: 5524213 (1996-06-01), Dais et al.
patent: 5588123 (1996-12-01), Loibl
Auve Glenn A.
Robert & Bosch GmbH
Striker Michael J.
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