CPU clock generator - for frequencies up to 10 MHz

for frequencies up to 10 MHz When using fast CPUs it can still be a problem to generate a good clock signal. By "good" we mean that it must have clearly defined high and low levels and it must be very sym- metrical. What we are thinking about, in particular, is 8 MHz CPUs but this circuit can operate with crystals of up to 20 MHz and, more importantly, it provides an excellent clock signal. The actual oscillator is based on a pair of inverters (N1 and N2) and it oscillates at twice the CPU fre- quency. Its signal is buffered by N3 and then the frequency is halved by D-type flip-flop FF1. The Q signal from this flip-flop is buffered and in- verted (by N4 and N5) and is then available for functions other than the CPU clock. The Q output, on the other hand, supplies the signal for the driver circuit for MOS levels that is based on T1 and T2. The clock signal finally output from this section FF1 = C1 10n 8 MHz 112 MHz) 116 MHz) IC2 = 74LS74 5V N2 IC1 1C2 11 N5 10 2 N 3904 NI ... N5 = ...