METHOD FOR TRANSMITTING DATA BETWEEN MICROCOMPUTERS

PURPOSE:To attain bidirectional data transfer by one data line, by supplying a time base of two microcomputers by a clock proportional to a power supply frequency, and outputting data at a frequency being 3 times the basic time base. CONSTITUTION:The microcomputers muCM4, 5 are connected to one common data line 1 via a bus driver 7 and a bus receiver 8, and an input data line and an interruption input line 6 are connected to the muCM4. A common base block generator 3 supplies a clock T having a frequency twice the power supply frequency and the clock is used as the basic clock for task control to the mu CM4, 5. The muCM5 performs data transfer start, outputs an LOW level to the muCM4 for synchronization of transfer and holds the level for the 3T. When the interruption is recognized by the muCM4, the data line is read after a prescribed time, and when the level is at LOW, the interruption is masked. The muCM5 transmits a transmission data for an interval of 3T, and after the muCM4 makes sampling in the interval of 3T, the transfer direction is switched by the method defined as a time axis.