| 摘要 |
PURPOSE:To improve the transmission efficiency even when number of external circuits is changed by providing an output device sending number of transmission permitting signals set in response to the number of the external circuits so as to vary the number of transmission permission signals sent in response to the number of connected external circuits. CONSTITUTION:The circuits is constituted that the number of sent transmission permission signal is limited via a transmission permission signal line 14 by a line number signal inputted from a transmission permission signal line number setting input line 16 in response to the number of connected external circuits 11. Thus, when three external circuits 11 are connected, a signal multiplex transmission LSI 12 sends sequentially periodically a transmission permission signal to the external circuits 11 only via the line 14 to assign the monopoly of a data bus 13, the sent data from the three external circuits 11 is received and multiplexed and a multiplex signal is outputted from a multiplex signal output line 15 as a serial signal. Since no ineffective transmission permission signal is sent, the transmission efficiency is improved and the data transfer period is shortened.
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