[sdiy] RE: Re: [sdiy] TB-303 cpu question - impossible

[Seb Francis]

the 303 cpu has nothing to do with the sound.  it only has to do with 
the sequencer and sequence memory.  the x0xb0x emulates only the sound 
generation circuitry of the 303 (from the widely available schematics), 
not the sequencer part.

seb


rdrake wrote:

>what about these guys: 
>
>http://www.ladyada.net/make/x0xb0x/index.html
>
>did they reverse engineer the cpu? sample the sound of a factory 303 and burn new roms? or are you talking about something completely different (i obviously don't know much about the guts of these machines, but i'm curious).
>
>b  
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>>----- ------- Original Message ------- -----
>>From: rw at firstpr.com.au
>>To: synth-diy at dropmix.xs4all.nl
>>Sent: Wed, 16 Nov 2005 09:52:12
>>
>>The TB-303 is a mask programmed 4 bit NEC CPU. 
>>There are no such CPUs
>>available, including as far as I know any such CPUs
>>with external ROM.
>>I don't think there could have been an external ROM
>>version, because it
>>would take most of the pins to access the ROM. 
>>Other than a special
>>device for development, I doubt if NEC ever made a
>>chip with all the
>>extra pins required for operation with an external
>>ROM.
>>
>>There is no way anyone knows of reading the ROM. 
>>Probably there is a
>>way of doing so as part of NEC's test procedure.
>>
>>So no-one has the object code.  The CPUs are not
>>available in any form.
>>Other CPUs in devices such as TR-606s have
>>different ROM data.
>>
>>Its my impression that a lot of talk about this
>>subject is not based in
>>reality, but on optimistic hopes that what happens
>>in completely
>>different situations might somehow apply to the
>>TB-303 CPU.
>>
>>It is technically possible to analyse the operation
>>of the CPU and to
>>create a new PCB to take its place, with some chip
>>like a PIC programmed
>>to emulate its functions.  That would be a huge
>>project.  For the actual
>>demand for CPU chips, which I guess in 12,000 or so
>>TB-303s in
>>existence, are failing at about one a week
>>somewhere in the world - it
>>is probably a lot easier to either write off the
>>TB-303, buy another
>>TB-303 and grab its CPU, or forget about the
>>sequencer and have a MIDI
>>In system installed.
>>
>>I have installed the Devil Fish mods, with MIDI In
>>for a TB-303 without
>>a CPU.
>>
>>  - Robin
>>
>>   http://www.firstpr.com.au/rwi/dfish/
>>    
>>
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