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

[Seb Francis]

p.s. I didn't mean that it stores the actual sequence memory itself - 
only that it has to do with this functionality.

Seb Francis wrote:

> 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 
>>  
>>
>>> ----- ------- 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/
>>>   
>>
>>
>>
>>  
>>
>