| 摘要 |
PURPOSE: A method for controlling congestion in a message transmission system is provided to prevent a message congestion state in a common bus by making each slave module generate a bus usage request if a required time should pass. CONSTITUTION: A user sets a prescaler value and an interval value and stores them in an interval value storage part(S61). A usage grant determination part reads the prescaler value and the interval value from the interval value storage part and stores them in its internal memory element. Then the usage grant determination part downcounts the stored prescaler value at regular intervals and updates the downcounted value into the present prescaler value(S62). The usage grant determination part judges whether the prescaler value is 0(S63). In case that the prescaler value is 0, the usage grant determination part decreases the interval value(S64) and judges whether the interval value is 0(S65). In case than the interval value is 0, the usage grant determination part concedes that a relevant slave module's bus usage request is valid, and executes bus usage arbitration(S66). In case that bus usage permission for the slave module is determined according the usage grant determination part's determination(S67), the slave module transmits messages through the bus(S68).
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