Hello friends.

Today I bring you something weird....

Being the connectivity freak I am, I have taken the schematics of one CPC speaking-machine interface and then I have adapted it to the EP... Not so difficult, as it only involves three chips.



You can click some links about the CPC interface, called Techni Musique - Synthetiseur Vocal.

https://hardware.speccy.org/temp/Amstrad-SV.html
https://gryzor.info/index.php/TMPI_speech_synthesizer
https://cpcrulez.fr/hardware-audio-synthetiseur_vocal_TMPI.htm
https://www.cpc-power.com/index.php?page=detail&num=4660

What has this MEA8000 chip interface of special compared to the usual speech interfaces based on the SP0256-AL2 chip?

Ok, both are 80's technology, don't expect clear conversation like these robots that answer us by phone today.

SP0256-AL2 was a self-contained chip with all the necessary to sound, it is for that it is inside almost all speech interfaces of the classic era, for almost all computers, even the rarest little one. Of course the Enterprise had its official approach, the Speakeasy.

But it is dull, it has a lot of allophones to mix, but always the same, so it sounds the same on every computer. A little Rom inside the chip contains all the sounds, so the quality is not great. Other drawback is that it doesn't release control (now talking about the Speakeasy Parallel port interface) until it has executed all the speaking string.

MEA8000 performs better than the ubiquitous SP0256-AL2, first because the dictionary of allophones is external to the chip, it can be even in Ram. Where the SP0256-AL2 only needs one byte to execute a sound, the MEA8000 needs to receive 4, but then it doesn't puts the Z80 to wait so, it is faster. Why 4 bytes?  it needs more information to talk because it can make a lot more complex sounds.

This was a French made interface, so you will find certain nasal accent in the voice...

But I am talking a lot without showing you a proof.....

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Link to video.

What I have done is to maintain the same CPC ports on this Enterprise interface, so then, when the original CPC software companion runs on marvellous Geco's  emulator,  these same ports are used but on EP hardware. This means that a lot of CPC software will run instantaneously on the Enterprise if only system calls are used....

The interface still has a lot of noise that I want to remove, but I wanted to share my results.

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Returning to my explanation, this was a French development, but the chip doesn't exclude the creation of other foreign allophones to add them to the list. Yes, because the dictionary is maintained on a simulated little Rom in Ram.

Was this chip only used in France?  No..... and here it comes the real surprise: it was used in a lot of other countries including Spain, mainly as university projects, and, know what? the MEA8000 chip also had Hungarian development....

At least I have found an amateur project that used it, the HomeLab/Aircomp/Brailab Z80 based computer(It even has an emulator). There are also some youtube videos about the MEA8000 that I can't understand... So I can't assure you that they are related to what I am trying to explain here.

Video 1
Video 2
Video 3

Is this MEA8000 chip still available at an affordable price? I think yes, I found it for 8€ the piece, up to 25€ on other web places, not a high price I think.

Amazing, isn't it?

I had little time for this project lately, but at last I have made it work without noise.

The correct schematic for the Enterprise is this one:

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It had some problems to fix, the most important was to remove the noise, adding a Z80 independent 4Mhz quartz. Yes, we already have a 4Mhz signal in the expansion bus, but it is not constant, because it is altered every time Dave stops the Z80 to draw something on video memory, thus disturbing the Speech chip frequency. I Asked some wise men here in Spain and they confirmed me that there are several computers that work this way, Spectrum, CPC, MSX and others, and usually it has been the case that a new project has reached an early version 2 development by only fitting an external clock...

Other problem was to follow the Enterprise rules for interfacing. Usually every external card comes fitted with a 74LS245 tristate buffer that only opens the Data bus when the card ports are accessed(decoded). This chip protects the Z80 from the possible Data bus "noise" that could come from the external peripheral.

The remaining problem was to find the optimum gain on the sound output, but I found it casually reading the French language book "Parole et micros", a bible about how to connect the MEA8000 chip to a lot of different micro computers(not the Enterprise, surprised?). It seems that the Enterprise has the same sound level gain than the MSX computers.


Ok, now I have the correct schematic and software to make it run(CPC emulator side), but now I need time and effort to learn how to make a PCB(Kicad). Usually I have asked aid to one of my friends, but now I can't continue boring them...

Ok, now I have the correct schematic and software to make it run(CPC emulator side), but now I need time and effort to learn how to make a PCB(Kicad). Usually I have asked aid to one of my friends, but now I can't continue boring them...

If it can wait a week or two, I’ll draw it for you. 🙂

VK