| 摘要 |
A serial data communication device of a half-duplex communication system includes two communication units. One of the communication units has a counter for measuring a length of a remaining time during one sending/receiving period set for one-way data transmission (a period during one sending/receiving period W from the time when the communication unit receives all the send data from the other communication unit to the time to start data sending). A send frequency in data sending is determined to as a lower value practicable in the range in which no collision of the data occurs, depending on the length of the measured remaining time. The other communication unit is configured so as to receive the send data of one communication unit to extract the send frequency in synchronization with a serial clock signal having the same frequency as the send frequency and send the data. Accordingly, send frequencies of the communication units associated with communication are automatically set to be as lower values as practicable depending on the distance of communication, so that effects of fluctuations in time such as jitter on the send data is reduced to a minimum.
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