https://oldwiki.cpcwiki.eu/api.php?action=feedcontributions&feedformat=atom&user=LaurentFrCPCWiki - THE Amstrad CPC encyclopedia! - User contributions [en]2026-08-29T10:15:24ZUser contributionsMediaWiki 1.25.1https://oldwiki.cpcwiki.eu/index.php?title=MEA8000_Unknown_Details&diff=110981MEA8000 Unknown Details2023-07-23T15:03:38Z<p>LaurentFr: </p>
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<div>[[Category:Electronic Component]][[Category:Music and sound]]<br />
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There are still a LOT of unknown details for the [[MEA8000]]. Since the chip is software programmable, it should be very easy to reverse-engineer that details - unfortunately, nobody did so, yet.<br />
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== Sawtooth and/or Noise ==<br />
* Theoretically, the device can output only <either> sawtooth <or> noise?<br />
* But, some block diagrams indicate that it can output both, added together?<br />
* Is there fade-out/fade-in switching from noise to sawtooth, or vice-versa?<br />
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== Sample Rate (and related values) ==<br />
* is sample rate (the actual sample output speed) 8000Hz or 8096Hz?<br />
* if it is 8000Hz, then exact sample rate would be 3.84MHz/3/160?<br />
* does P register overflow after 8000 or 8096 steps?<br />
* are fm_cos and bw_exp values using divider 8000 or 8096?<br />
* are the P and PI values in table correct (in case 8000 and 8096 are mixed)?<br />
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== Filters ==<br />
* is EXP formula using "-1*pi" (mess emulator) or "-2*pi" (datasheet)?<br />
<br />
== Continue Mode ==<br />
* is repeated frame using FD=unchanged or FD=0 (=faster reactions)?<br />
* is repeated frame using PI=unchanged (=can "run out of control")?<br />
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== Slow-Stop Mode ==<br />
* can one "resurrect" by sending data when already in "stopping" phase?<br />
* does the hardware discard <incomplete> frames on slowstop?<br />
* works exactly as when resending the current frame but with AMPL=0?<br />
* are FD and PI kept unchanged?<br />
<br />
== Random Generator (Noise) ==<br />
* works how exactly?<br />
<br />
== Interpolations ==<br />
* does it take the whole FD period (8..64ms) to reach new target value?<br />
* - AMPL is interpolated on the translated values (eg 0.707)?<br />
* - FM/BW are interpolated on the COS/EXP values?<br />
<br />
== Status Register ==<br />
* REQ=0 occurs for 3us after 1st..3rd Frame byte (correct)?<br />
* REQ=0 occurs for up to 8..64ms after 4th Frame byte (really/always)?<br />
* REQ=0 occurs for up to 8ms after Initial Pitch (really/why)?<br />
* is it REQUIRED to send new data during ACTIVE output (to prevent slowstop)?<br />
* is it IMPOSSIBLE to send new data during ACTIVE output (datasheet says so)?<br />
<br />
== DAC ==<br />
* is there saturation occuring in case samples exceed 8bit range, and when?<br />
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== Clock Source ==<br />
* can be external crystal, or external TTL, or what... an external <loop>?<br />
<br />
== Specifications ==<br />
* does this doc exist in internet: "MEA8000 voice synthesizer: principles and interfacing, Philips Technical Publication 101" (Philips/Elcoma 1983)?<br />
Answer : http://zx81.ordi5.free.fr/vtr/download/MEA8000-2.pdf</div>LaurentFr