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<TITLE>RE: SV: TB-303 original power supply - Answerfrom author</TITLE>
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<P><FONT SIZE=2>> -----Original Message-----</FONT>
<BR><FONT SIZE=2>> From: Trevor Page [<A HREF="mailto:trevor@resonance.fsnet.co.uk">mailto:trevor@resonance.fsnet.co.uk</A>]</FONT>
<BR><FONT SIZE=2>> Sent: Friday, August 04, 2000 9:52 PM</FONT>
<BR><FONT SIZE=2>> To: *Star Project; DIY skicka Lista</FONT>
<BR><FONT SIZE=2>> Subject: Re: SV: TB-303 original power supply - Answerfrom author</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> Hi Andreas and all,</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> Regarding the sequencer - just a reminder that the TB303's custom</FONT>
<BR><FONT SIZE=2>> microcontroller is no longer available, not even from Roland </FONT>
<BR><FONT SIZE=2>> and therefore</FONT>
<BR><FONT SIZE=2>> it will not be possible to clone the sequencer exactly. New </FONT>
<BR><FONT SIZE=2>> firmware will</FONT>
<BR><FONT SIZE=2>> have to be written for a modern device, eg PIC / Atmel. Since </FONT>
<BR><FONT SIZE=2>> you mention</FONT>
<BR><FONT SIZE=2>> the memory circuit, I presume you are intending to clone the </FONT>
<BR><FONT SIZE=2>> sequencer.</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> > However the battery supply still has to included</FONT>
<BR><FONT SIZE=2>> > so that it works the same way since the memory</FONT>
<BR><FONT SIZE=2>> > depends on the battery supply.</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> This will not be necessary, since a modern sequencer clone is </FONT>
<BR><FONT SIZE=2>> unlikely to</FONT>
<BR><FONT SIZE=2>> use volatile static-RAMs. Rather, modern EEPROM devices will </FONT>
<BR><FONT SIZE=2>> be used which</FONT>
<BR><FONT SIZE=2>> do not require the use of a backup supply. Your power supply </FONT>
<BR><FONT SIZE=2>> circuit would</FONT>
<BR><FONT SIZE=2>> not need to provide a backup supply line from the battery.</FONT>
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<P><FONT SIZE=2>Somewhere in the future I'm planning to clone the sequencer, it cannot really be difficult to do.</FONT>
<BR><FONT SIZE=2>E2PROMs have a limited number of writecycles, 100.000 cycles guaranteed for most devices. The firmware needs to take account of that, probably just writing the E2PROM on power down. The hardware must include some big capacitor to keep the processor running for a while after power down. I would still prefer some static RAM. E2 is more interesting for information that does not change that often, configuration or calibration data for example.</FONT></P>
<P><FONT SIZE=2>JJ</FONT>
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