On 23 abr, 19:31, Rich Webb wrote:
Hold it in a reset state longer on startup. These guys are unusual in
that their RST pin is active high, so keep that in mind.

The naive way to implement reset in this family is just a cap to the
positive supply rail, a resistor to ground, and the RST pin in between.
If this is what they used, it sounds like you're just on the edge of
reliability and may be able to make it happy by boosting the RC time
constant a tad by using a larger C or R, depending on which is easier to
get to.

There are also "supervisory" chips that are more reliable and can also
take care to reset on brown-outs. Some of these hold reset active for a
fixed interval but, IIRC, some set the time with an external R or C.

--
Rich Webb * * Norfolk, VA

Thank you for the replies.
I tried to keep the reset input active manually for several seconds
but still behaves the same. What happens while RST is high is the
micro sets some outputs high and turns on all the hardware. When I
remove RST all comes back to st-by. From then on the behaviour is the
same. For reset it uses a KIA7436P:
http://www.alldatasheet.com/datashee.../KIA7436P.html