Clock Circuit

A project log for Novasaur CP/M TTL Retrocomputer

Retrocomputer built from TTL logic running CP/M with no CPU or ALU

Alastair HewittAlastair Hewitt 05/09/2019 at 02:350 Comments

The clock circuit consists of a Pierce Oscillator running at 30.875 MHz and two Johnson Ring Counters. The first ring counter (mclk/nclk) consists of a single flip-flop to divide the 30.875 MHz dot clock (dclk) down by a factor of 2. The second (pclk/qclk) consists of two flip-flops to divide the dot clock down by a factor of 4. The last stage of this counter is duplicated to provide an additional set of identical clocks.

Some considerations in this design:

The following shows the clocks generated by the circuit above. The tclk is also included for reference, but not shown in the circuit.