Digital tips for CircuitMaker

Speed

The speed of the digital simulation is set under Options, Digital Options, Simulation speed. For counter circuits, a speed of 7 to 10 is appropriate.

Building counters with JK Flip-flops

I suggest using the 7473 1/2 (half of a dual jk flipflop). Be sure to tie the R input to +5 volts or a logic 1. If you use the 74LS112, both the S and R inputs need to be tied to +5 volts. See the Texas Instruments link on the main Electronics page for data sheets. One of the more convenient to use is the 7473 1/2, which is half of the 7473 chip. This is nice because it only has one JK flipflop rather than two. This makes our circuits look simpler.
Use the Logic Display (under Hotkeys1) for a readout.

Here is a synchronous divide-by-four circuit using a 7473 1/2 flip flop. The logic switch is set to 0 to reset the flip flops to zero and set to 1 to let them run:

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