View source for MEA8000 Unknown Details

[[Category:Electronic Component]][[Category:Music and sound]]

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.

== Sawtooth and/or Noise ==
* Theoretically, the device can output only <either> sawtooth <or> noise?
* But, some block diagrams indicate that it can output both, added together?
* Is there fade-out/fade-in switching from noise to sawtooth, or vice-versa?

== Sample Rate (and related values) ==
* is sample rate (the actual sample output speed) 8000Hz or 8096Hz?
* if it is 8000Hz, then exact sample rate would be 3.84MHz/3/160?
* does P register overflow after 8000 or 8096 steps?
* are fm_cos and bw_exp values using divider 8000 or 8096?
* are the P and PI values in table correct (in case 8000 and 8096 are mixed)?

== Filters ==
* is EXP formula using "-1*pi" (mess emulator) or "-2*pi" (datasheet)?

== Continue Mode ==
* is repeated frame using FD=unchanged or FD=0 (=faster reactions)?
* is repeated frame using PI=unchanged (=can "run out of control")?

== Slow-Stop Mode ==
* can one "resurrect" by sending data when already in "stopping" phase?
* does the hardware discard <incomplete> frames on slowstop?
* works exactly as when resending the current frame but with AMPL=0?
* are FD and PI kept unchanged?

== Random Generator (Noise) ==
* works how exactly?

== Interpolations ==
* does it take the whole FD period (8..64ms) to reach new target value?
*  - AMPL is interpolated on the translated values (eg 0.707)?
*  - FM/BW are interpolated on the COS/EXP values?

== Status Register ==
* REQ=0 occurs for 3us after 1st..3rd Frame byte (correct)?
* REQ=0 occurs for up to 8..64ms after 4th Frame byte (really/always)?
* REQ=0 occurs for up to 8ms after Initial Pitch (really/why)?
* is it REQUIRED to send new data during ACTIVE output (to prevent slowstop)?
* is it IMPOSSIBLE to send new data during ACTIVE output (datasheet says so)?

== DAC ==
* is there saturation occuring in case samples exceed 8bit range, and when?

== Clock Source ==
* can be external crystal, or external TTL, or what... an external <loop>?

== Specifications ==
* does this doc exist in internet: "MEA8000 voice synthesizer: principles and interfacing, Philips Technical Publication 101" (Philips/Elcoma 1983)?
Answer : http://zx81.ordi5.free.fr/vtr/download/MEA8000-2.pdf