Hi,

Conny wrote:

>
>  Mauricio,
>  You could try to power your PIC from the telephone line (3.5V) and control
>  the supply voltage to the DTMF receiver (5V) from one port pin on your PIC.
>  I have used 3V logic with 5V logic without problems (CMOS).
>  Use as low resonator frequency as possible (maybe 32kHz) to decrease power
>  consumption. You may also use the sleep-powerup feature in the PIC.
>

Hmmm... I think that controlling 5V logic with 3V will work OK, but what if
you need to read something from this 5V device by a 3V PIC? Isn't there a
chance to blow something (from the datasheets, PIC I/O pins are rated
to max. Vdd+0.6V)?

Mauricio CULIBRK

ARNE Computers d.o.o.
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