Logic Circuits for Computer Education in Junior High School

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a) Logic Elements by TransistorsIn order to show that logic ICs can be made from transistors and not to treat then as "black box", NAND, NOR.and NOT elements are composed of 2 or 1 transistors by the method of DCTL (Direct Coupling Transistor Logic). They are not TTL type, but, the principle is easy to understand.b) HFL CheckerH and L mean High(1) and Low(0) logic levels, respectively. F means electrical float state or no input state to IC input terminals. This developed HFL checker can differentiate this 3 states in order to detect circuit conditions. This checker is composed of 1 transistor and 1 NOT element in principle.c) TTL Pulse Oscillator with Period 1 sec.In various experiments on logic circuits, TTL oscillator with low frequency is. useful for observing releated results with eyes. The 50 Hz signal from a power line is reduced to TTL 1Hz signal by using transformer, diode, NOT and counter(50).d) Checker for "Which has switch A and B been pressed quickly? "In a simple RS-FF with 2 NORs, R=S=1 are forbidden because of a racing phenomenon etc.. But, this phenomenon means that a quicker response to R/S terminal can be checked. This idea is expaded in this checker. Since this checker has the fundamental 5 mechanisms of computer(input, output, computation, memory, control), we can say that this is a "computer" in spite of a simple structure.e) Measuring by/Control to Digital OscilloscopeBy using RS232C interfaces between a digital oscilloscope and a personal computer, the application tool for measuring by and contolling to digital oscilloscope is developed in order to observe signals from electric and logic circuits. Signal processing, data saving/loading and printing out etc. are enable.