Data communication system and electronic control unit used therein
First Claim
1. A data communication system comprising:
- a common data bus; and
a plurality of electronic control units, each including a central processing unit for controlling an electronic device and communication means, connected to the common data bus, each electronic control unit communicating with other electronic control units under a predetermined data transmission protocol through the common data bus, the communication means forming a communication frame that includes a message to be transmitted and other information necessary to transmit the message to other electronic control units;
wherein a length of the message is variable;
wherein the message is placed between a signal indicating the length of the message and an error check code, and a signal indicating an end of the message is placed immediately after the error check code; and
wherein the message, the signal indicating the length of the message, and the error check code are coded according to a predetermined coding rule, and the signal indicating the end of the message is coded according to another coding rule, the other coding rule violating the predetermined coding rule.
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Accused Products
Abstract
In a data communication system in which many nodes are connected to a common data bus so that each node can communicate with other nodes, a data frame to be transmitted from a node to other nodes includes a message having a variable length interposed between a signal indicating the length of the message and a signal indicating the end of the message in the frame. The message and the signals are coded according to a coding rule such as NRZ, and a bit stuffing rule is applied to the signal indicating the length of the message and the message while another rule violating the bit stuffing rule is applied to the signal indicating the end of the message. When the message length is changed due to noise or other causes in the course of data transmission, the signal indicating the end of the message is clearly detected at a receiving end because it is coded according to a rule different from the rule applied to the message and other signals. Further, since the length of the message actually received at the receiving end can be compared with the signal indicating the length of the message, transmission error can be detected without fail.
28 Citations
8 Claims
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1. A data communication system comprising:
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a common data bus; and a plurality of electronic control units, each including a central processing unit for controlling an electronic device and communication means, connected to the common data bus, each electronic control unit communicating with other electronic control units under a predetermined data transmission protocol through the common data bus, the communication means forming a communication frame that includes a message to be transmitted and other information necessary to transmit the message to other electronic control units; wherein a length of the message is variable; wherein the message is placed between a signal indicating the length of the message and an error check code, and a signal indicating an end of the message is placed immediately after the error check code; and wherein the message, the signal indicating the length of the message, and the error check code are coded according to a predetermined coding rule, and the signal indicating the end of the message is coded according to another coding rule, the other coding rule violating the predetermined coding rule. - View Dependent Claims (2, 3, 4, 5, 7)
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6. An electronic control unit connected to a common data bus, the electronic control unit communicating with other electronic control units also connected to the common data bus under a predetermined transmission protocol through the common data bus, the electronic control unit comprising:
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a central processing unit for controlling an electronic device; and communication means for forming a communication frame that includes a message from the central processing unit to be transmitted to other electronic control units and other information necessary for the message transmission; wherein a length of the message is variable; wherein the message is placed between a signal indicating the length of the message and an error check code, and a signal indicating an end of the message is placed immediately after the error check code; and wherein the message, the signal indicating the length of the message, and the error check code are coded according to a predetermined coding rule, and the signal indicating the end of the message is coded according to another coding rule, the other coding rule violating the predetermined coding rule. - View Dependent Claims (8)
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Specification