Dr Skip wrote:
> Microchip seems to agree. From their support:

Do they ?

> 
> -------------
> Read-modify-write can cause that.  I strongly recommend never bit setting or 
> clearing a port.  You should always read the port,...

I thought we agreed on that it is the *reading* of the
port that is the potential source of RMW problems...

Jan-Erik.


  copy it to ram, modify the
> bit, then write that back out to the whole port.  Since the PIC is trying to 
> change all 8 bits (even if some are the same), this prevents it from reading 
> the other bits and changing them.  You can learn more about read-modify-write 
> by searching our knowledge base.
> 
> The PIC18 gets around this by having an output "LAT"ch register.  If you bit 
> set LATB,3 for example, then only that pins output register is set, the others 
> are not read from the outside world or modified.
> 
> Finally, watch out for capacitive loading on pins.  If a pin is strongly 
> capacitive, it could be read incorrectly due to the capacitance holding the pin 
> state.  When read incorrectly, it is also written in


correctly.  Again, using
> the method mentioned above should assist with this issue as well.
> --------------
> 
> 
> Wouter van Ooijen wrote:
>> I definitely do advocate using shadow registers. 
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