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5 bytes added, 12:03, 13 October 2010
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The '''AY-3-8912''' is a sound generator that is built-in on several 128 KB models of the [[ZX Spectrum]] and in the [[Timex TS20682000 series|Timex Sinclair 2068]], but can also be found in several peripherals, such as the Fuller Box an the Melodik interface.
The 128K's AY chip is clocked at 1.7734 MHz (to within 0.01%). Writing to port FFFDh (65533) selects a register, and reading from port FFFDh reads that register's contents. Writing to port BFFDh (49149) writes new data to the currently selected register. On the 128K/+2, reading from BFFDh will return the [[floating bus]] value as normal for unattached ports, but on the +2A/+3, it will return the same as reading from FFFDh. The Melodik interface uses the same ports as the 128K.

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