The animated gif was produced by a Java program (contact me for source code) the original cellular automaton pattern was created by Renato Nobili renato.nobili@pd.infn.it and lifted from the Golly simulator.

Read arm demo. Author: Renato Nobili <renato.nobili@pd.infn.it>

Controls are provided to direct the read arm (r-arm). Set the machine running at a slow speed to see it working.

A pulse on the input line (IN) causes the pattern to send one of two signal-trains down the output line (OUT), depending on the presence (1) or absence (0) of a mark on the tape at the current position. The reading head then moves forward, ready to read the next cell.

As with the construction arm, OTS (blue) and STS (red) lines work together to manipulate the cells at the end of the read arm. Various coders (C) and decoders (D) are used to send the required signal trains, which depend on the output of the read operation since the read head is left in one of two states.

Other controls (not shown) are needed to retract the read-arm.

http://www.pd.infn.it/~rnobili/wjvn/index.htm http://www.pd.infn.it/~rnobili/au_cell/ http://en.wikipedia.org/wiki/Von_Neumann_universal_constructor http://en.wikipedia.org/wiki/Von_Neumann_cellular_automata

Originally distributed as: RW-ARM_ADV.JVN