Andrew E. Kalman <PICLIST@mitvma.mit.edu> wrote:

> Seriously, though, simplify your code on the way to a solution. Use
> this instead:
>
> void main()
> {
>         /* initialization code  */
>
>         while (1)
>         {
>                 PORTA ^= 0x10;
>         }
> }

Andrew:

Personally, I think that's a bad suggestion.

Explicitly writing 1's and 0's, as Roy originally did, ensures that
he's not having a read-mofdify-write problem... Which he WOULD have
had if he used your code with his original hardware (i.e., without a
pullup on RA4).

Without that pullup, RA4 would always read low, so your code would
just repeatedly write a 1 to the pin.  With a too-weak pullup, your
code would have the somewhat-interesting effect of auto-adapting his
toggle frequency to the time-constant of his resistor... But that
probably isn't what he wanted, and it would likely confuse him to see
a very asymmetrical waveform with a frequency much lower than he
expected.

-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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