Roman Black <PICLIST@mitvma.mit.edu> wrote:

> has anyone had trouble using the internal RC oscillator on the
> lower PICs, like the 12c508 or 16c505 ??
> ....
> Vdd rises to full +5v in less than 150mS.

then

> I assumed that Microchip knew their stuff and when you set a PIC
> to internal RC osc and internal MCLR control this would be ok.
> After all, it's not hard to start up an RC osc is it?

Roman:

The failure of the RC oscillator is just a symptom of your REAL
problem, which is either that your Vdd rise time is too long or that
Vdd isn't starting its rise from < 0.7V.

You only characterized your rise time as "less than" 150 ms. I don't
have a datasheet here, but I recall that Microchip's specified
Minimum Vdd Rise Rate is 0.05V/ms.

Are you sure that your PIC's power supply is dropping to below 0.7V
before you switch it on?

-Andy


=== Andrew Warren --- aiw@cypress.com
=== IPD Systems Engineering, CYSD
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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