Strange Behavior in setting several pin outputs states.

[kappuz]

I want to thank you very much.

The problem is resolved, now I am setting the pin output states super fast!

The final working code was the one posted by rmteo, but thank you all really!


ShadowC VAR byte
ShadowC = PORTC

ShadowC.0 = 1
PORTC = ShadowC

ShadowC.1 = 1
PORTC = ShadowC

ShadowC.2 = 1
PORTC = ShadowC

ShadowC.3 = 1
PORTC = ShadowC

[HenrikOlsson]

You can do it even faster by doing it the way Charles originally showed you, (did you REALLY try that and it didn't work?) in other words:

ShadowC VAR BYTE
ShadowC = PortC

ShadowC.0=1
ShadowC.1=1
ShadowC.2=1
ShadowC.3=1

PortC = ShadowC

/Henrik.

[rmteo]

You can do it even faster by doing it the way Charles originally showed you, (did you REALLY try that and it didn't work?) in other words:

ShadowC VAR BYTE
ShadowC = PortC

ShadowC.0=1
ShadowC.1=1
ShadowC.2=1
ShadowC.3=1

PortC = ShadowC

/Henrik.

Even faster would be this way - but obviously the OP did not try it the way Charles described.

ShadowC VAR BYTE
ShadowC = PortC

ShadowC.0 = $F

PortC = ShadowC

[rmteo]

Sorry for the typo - and the inability to edit a post.

ShadowC VAR BYTE 
ShadowC = PortC  

ShadowC = $f 

PortC = ShadowC

[HenrikOlsson]

Hi,

Even faster would be this way - but obviously the OP did not try it the way Charles described.

Not really because then the top four bits will be 0 which they might not have been when PortC was read. And IF the top four bits doesn't matter then I see no reason for not simply writing to PortC directly, ie PortC = $F which would make THIS particular example even faster....

However, I suspect that setting the low four bits to 1 are just an example. Using bitwise AND/OR could also work but I'm not sure it's faster than simply flipping the four bits in ShadowC and then writing it to the port.

/Henrik.

[rmteo]

All of this is basic stuff - using a bit mask and writing directly to PORTC is the fastest way. Bottom line is that the OP did not do it the way Charles described and that is why it did not work for him. I just re-wrote it in a way that I felt would make sense to the OP.

[NickMu]

One of the best threads dealing with RMW and solutions to solve the problem is here:

http://www.picbasic.co.uk/forum/showthread.php?t=15843

Charles also explains that using this method should not affect your USART pins if they are on that particular port.

Just out of curiosity, is this method affecting your PWM if it is active on the same port and how?
Are there any other special or ordinary functions that could be affected?
I’m especially interested to know about inputs on the port that might be used for interrupts and the external source changes while this action is in progress.

Regards,

Nick