...electronics

TECHNICAL ELECTRONICS NOTES: The FPGA and its interface to the PC, the tone generator, and the analogue integrator all reside comfortably on a single full-length card plugging into the AT (ISA) Bus of the PC. The analogue integrator was of the basic op-amp/resistor/capacitor type, with a MOSFET to reset it to zero [7]. A MC68HC11A0 micro-controller operated this reset signal (and that of the FPGA), and performed 8-bit A/D conversion on the integrator output. A final accuracy of 16 bits in the integrator reading was obtained by summing (in software) the result of integration over 256 sub-intervals, with an A/D conversion followed by a resetting of the analogue integrator performed after each sub-interval. The same micro-controller was responsible for the generation of the tone.

Locations in the configuration memory of the FPGA and in the dual-port RAM used by the the micro-controller could be read and written by the PC via some registers mapped into the AT-Bus I/O space. The XC6216 requires some small but non-trivial circuitry to allow this - schematics are available from the author.

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...modules.

See [14, 13] for an expansion of this argument and earlier experiments specifically designed to explore the feasibility of such unconstrained evolution.

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