[sdiy] VCDO using PIC16C771

[jean-pierre.desrochers at ville.quebec.qc.ca]

>It seems to me that, for this application, 4 kB of RAM would be
>more useful than 4 kB of EEPROM. You will have to update the
>note-number-to-DAC-value table continuously because of temperature
>drift and EEPROMs can only take so many cycles.

The idea was that the lookup table / PIC combination would keep
the pitch stable even when the XR2206 drifts.
That's where the fixed EEPROM table comes in. 

>Yes, with RAM, you'll need to initialise the table at power on,
>but you would have the same problem with an EEPROM ; chances are
>the data in the EEPROM is for a warm device.

Think of the size of the cpu ROM code "embedded lookup table"!!
This would take at least 3Kbytes of valuable ROM. 
Even with a big log formula to calculate each RAM cells.
No startup filling RAM routine, the EEPROM has already
the log values for the VCO XR chip to stay in tune
with the help of the PIC. 
The idea is to keep less component and small code size.

J-P Desrochers
Quebec City