| 摘要 |
PURPOSE:To make the mode designation change disable during data transmission by making the setting of a mode designation effective in response to a reset signal or an overflow signal from a central processing unit and making similarly the setting of the mode designation ineffective in response to a transfer start signal. CONSTITUTION:The data transmitter consists of a transfer register 10, a transfer counter 11, a flag circuit 12, a mode control circuit 13 and an AND gate 14. After a reset signal 107 and a transfer start signal 108 from a host device are inputted, the transfer device is released from the control of the host device and the host device outputs a mode designation signal 111 asynchronously with the operation of the transfer device. Then a flag holding circuit 12 is in the set state by the signal 108 and since an internal gate is closed in this state, no mode designation signal 111 is received and the mode signal 112 is unchanged. Thus, the data transfer is progressed according to the mode set previously.
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