| 摘要 |
PURPOSE:To increase an effective data transmission speed by comparing the data within a buffer memory with input/output signals and transfers signals only when no coincidence is obtained from said comparison. CONSTITUTION:The input signals of input/output devices b1-bn are read out successively via a switch circuit 5 by a command of a control circuit 3 and then written to a buffer memory 4. At the same time, the contents of the memory 4 stored previously by a cycle are also read out. A discordance detecting circuit 7 compares those input signals with the contents of the memory 4. The signals ''0'' and ''1'' are supplied to a discordance deciding memory 8 when the coincidence and discordance are obtained from said comparison respectively. Then the circuit 3 reads out successively the contents of the memory 4 and sends them to a transmission line 2 after P/S conversion performed via a signal converter 1. Then the contents of the memory 8 are referred to successively, and the contents of the corresponding memory 4 are transmitted to the line 2 only when the contents of the memory 8 is equal to ''1''. While no contents of the memory 4 is transmitted to the line 2. In other words, the transmission of data is carried out only when the input signal has a change. In such a way the effective data transmission speed is increased. |
