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Last modified on 17 December 2010, at 16:06

MEA8000 Unknown Details

Revision as of 16:06, 17 December 2010 by MacDeath (Talk | contribs)


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)?