toughy / ppg etc

[Paul Maddox]

Peter,

>Dear Paul 
>firstly congratulations for having some of your music released !

thanks...

>there are a number of "standards " for saving data [on cassette ?]
>that were used on the early computer systems .
>Its possible that the ppg uses one of them.

yep, it had a tape interface... From what I understand it has a 
constant tone, then a 10101010 train to set the timing, and then comes 
the data.

>I think I have more details in a book on computer interfacing.
>this would enable you to decode it into a binary file ?  

yep, please.....

>but its how the data relates to the waveforms that's dificult to work
>out.
>I've looked through what  ppg info I have here , and it doesn't give 

any
>clues as to what format is used.

8 bit waves, half cycles. if I could get it into 1's and 0's I would 
be happy enough... I spent 3 days getting what I have from the PPG 
eproms, so I dont mind playing for a couple of weeks if I need to.

>but it seems to say that two eproms were used for the wavetables 

[called
>eprom 4 and 6 ? ] on the 2.3 
>

yep, It does and it doesn't.... the eproms you mention have data on, 
some of what would appear to be preset waveforms (127 8 bit half cycle 
waveforms) these I have expanded to full cycle waveforms and are in my 
modular as a PPG VCO (1v/oct) and CV selection of wave.

Acording to the service guide/schematic (yes I found one at last) it 
has a bank of ram chips which are used , as the schemtic describes it, 
for 'wave table ram containg 2048 waves approx.'... I assume you could 
pick one or more of the 'preset' waves (127) and create your own table 
in ram (battery backed).

>hopefully someone else on the list has the necesary info.
>regards Peter 
>South London England
>
Thanks for the help..

Paul Maddox


 
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