Turing Trains

 

computational train track layouts

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Functions using Flip-flops

We can construct a flip-flop using two linked lazy points and a sprung point.

Trains arriving on the main line (from the right) pass up to an inverter loop and 'flip' (invert) the flip-flop. They then exit via the lower lazy point on alternating branch lines.

Flip-flop Distributor
flip flop point
Click layout to pause/run train. Click start to reset train.

Adam Chalcraft and Michael Greene in their paper 'Train Sets' name the flip-flop circuit as a 'Distributor'.
Also see equivalent circuits and Duplo page for a flip-flop Duplo layout.

In theory, all functions can be constructed using flip-flops alone, but this can require many more points. Also, as each flip-flop requires 3 points to build, they are not the most efficient way to create many functions.

Flip-Flop Count Up (increment)

Connecting flip-flops in series creates a Count Up (increment) circuit. This has the same operation as Count Up function. The layout is similar to an Inverter function.

Flip-flop Count Up (incrementor)
flip-flop counter
Click grass to pause/run train Click points to switch 0/1 Click start to reset train/points

The train increments the counter and returns back along the same track. The counter rolls over from 7 (111) to 0 (000).

Compact Flip-Flop Count Up (increment)

A more compact flip-flop can be built using three linked lazy points. The central point is drawn reflected.

This counter is shown with an overflow line instead of rolling over.

'Compact' Flip-flop Counter Up
compact flip-flop counter
Click grass to pause/run train Click points to switch 0/1 Click start to reset train/points

Compact Flip-Flop Inverter

This layout inverts register A. The flip-flops are shown without the short vertical track between lazy points, which remain linked together. Also see Subtract function.

'Compact' Flip-flop Inverter
compact flip-flop inverter
Click grass to pause/run train Click points to switch 0/1 Click start to reset train/points

Turing Trains | cr31.co.uk | 2017

 

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