| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit for monitoring and detecting a data transfer protocol error occurring in asynchronous data transfer through a data bus. SOLUTION: This circuit monitors bus request/affirmative answer control lines 53 and 56 based upon a predetermined handshake protocol. If an illegal logical state which is not defined or illegal for the bus request control line 53 or affirmative answer control line 56 is detected, this circuit gives an error value to a data transmission entity. The data transmission entity is capable to retry data transmission through the data bus as a result of receiving the error value.
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