Difference between revisions of "MEA8000 Unknown Details"
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(Created page with '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 …') |
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| − | Sawtooth and/or Noise | + | [[Category:Electronic Component]][[Category:Music and sound]] |
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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. | ||
| + | |||
| + | == Sawtooth and/or Noise == | ||
* Theoretically, the device can output only <either> sawtooth <or> noise? | * Theoretically, the device can output only <either> sawtooth <or> noise? | ||
* But, some block diagrams indicate that it can output both, added together? | * 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? | * Is there fade-out/fade-in switching from noise to sawtooth, or vice-versa? | ||
| − | Sample Rate (and related values) | + | == Sample Rate (and related values) == |
* is sample rate (the actual sample output speed) 8000Hz or 8096Hz? | * 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? | * if it is 8000Hz, then exact sample rate would be 3.84MHz/3/160? | ||
| Line 11: | Line 15: | ||
* are the P and PI values in table correct (in case 8000 and 8096 are mixed)? | * are the P and PI values in table correct (in case 8000 and 8096 are mixed)? | ||
| − | Filters | + | == Filters == |
* is EXP formula using "-1*pi" (mess emulator) or "-2*pi" (datasheet)? | * is EXP formula using "-1*pi" (mess emulator) or "-2*pi" (datasheet)? | ||
| − | Continue Mode | + | == Continue Mode == |
* is repeated frame using FD=unchanged or FD=0 (=faster reactions)? | * is repeated frame using FD=unchanged or FD=0 (=faster reactions)? | ||
* is repeated frame using PI=unchanged (=can "run out of control")? | * is repeated frame using PI=unchanged (=can "run out of control")? | ||
| − | Slow-Stop Mode | + | == Slow-Stop Mode == |
* can one "resurrect" by sending data when already in "stopping" phase? | * can one "resurrect" by sending data when already in "stopping" phase? | ||
* does the hardware discard <incomplete> frames on slowstop? | * does the hardware discard <incomplete> frames on slowstop? | ||
| Line 24: | Line 28: | ||
* are FD and PI kept unchanged? | * are FD and PI kept unchanged? | ||
| − | Random Generator (Noise) | + | == Random Generator (Noise) == |
* works how exactly? | * works how exactly? | ||
| − | Interpolations | + | == Interpolations == |
* does it take the whole FD period (8..64ms) to reach new target value? | * does it take the whole FD period (8..64ms) to reach new target value? | ||
* - AMPL is interpolated on the translated values (eg 0.707)? | * - AMPL is interpolated on the translated values (eg 0.707)? | ||
* - FM/BW are interpolated on the COS/EXP values? | * - FM/BW are interpolated on the COS/EXP values? | ||
| − | Status Register | + | == Status Register == |
* REQ=0 occurs for 3us after 1st..3rd Frame byte (correct)? | * 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 8..64ms after 4th Frame byte (really/always)? | ||
| Line 39: | Line 43: | ||
* is it IMPOSSIBLE to send new data during ACTIVE output (datasheet says so)? | * is it IMPOSSIBLE to send new data during ACTIVE output (datasheet says so)? | ||
| − | DAC | + | == DAC == |
* is there saturation occuring in case samples exceed 8bit range, and when? | * is there saturation occuring in case samples exceed 8bit range, and when? | ||
| − | Clock Source | + | == Clock Source == |
* can be external crystal, or external TTL, or what... an external <loop>? | * can be external crystal, or external TTL, or what... an external <loop>? | ||
| − | Specifications | + | == Specifications == |
| − | * does this doc exist in internet: "MEA8000 voice synthesizer: principles and | + | * 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 | |
Latest revision as of 10:03, 23 July 2023
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.
Contents
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?
- 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
