parallel output

[nailuy]

Hy guys, I have misunderstanding:
I fount on net this operator !! (two bonded logical negation) what is mean?

also my question is:
How to put variable value on parallel output?

[Ttelmah]

Simply use output_b(var);

Can't get much simpler.....

The bit output, would work, but be much slower, but do a search here for the RMW problem (search here for this term). This depends on what is actually connected to your output pins.

As a comment though is var & 2 (for example), ever going to be '1' (the value required by the output_bit function?. This relates to your !! question....

Double negation, is sometimes used as a way of converting a numeric value to a logical (0/1) value. Negation in C, returns TRUE depending on a value being zero. Negate again, and you have TRUE when a value is non zero. Generally !=0, is easier to understand, and gives the same truth table.

Best Wishes

[nailuy]

Thanks Ttelmah.

But if I want to use:
B7 C2 A5 B6 B1 C3 B0 C0
0 0 0 0 1 1 1 1

and:

RMW problem I try to search and nothing to find.
Do yu have title for that post?

I try:
output_bit(PIN_B0, !!(var & 1));
output_bit(PIN_B1, !!(var & 2));
output_bit(PIN_B2, !!(var & 4));
output_bit(PIN_B3, !!(var & 8));
output_bit(PIN_B4, !!(var & 16));
output_bit(PIN_B5, !!(var & 32));
output_bit(PIN_B6, !!(var & 64));
output_bit(PIN_B7, !!(var & 128));

and again not working.

I'm beginner and some signs I'm not understandings.
Best regards .

[PCM programmer]

Post a complete, compilable test program. That means, post the #include
for the PIC, #fuses, #use delay(), and #defines, variable declarations,
and main(). Also post your compiler version.

Then we can see what you are doing and maybe offer help.

[Ttelmah]

A search for RMW, finds dozens of posts about this.

<http://www.ccsinfo.com/forum/viewtopic.php?t=42268&highlight=rmw>

Is a good start since it points to a number of others.

[Ttelmah]

Lets add something here.

The code you've posted now, _will_ work, unless you have another problem. RMW, is the most likely, however could be something 'silly' to do with your code or hardware.
Though it'll work, there is a more elegant way of doing this using a CCS function:

output_bit(PIN_B0, bit_test(var,0));

etc..
Used with a constant, the compiler codes 'bit_test', to use the single instruction 'BTFSC' (bit test in F, skip if clear). Saves two instructions on each output.

So start at the beginning. Have you proved that you can do something much simpler (toggling a single pin), and your processor is running, and at the correct speed.

If it still fails, simplify. Just the fuses, and a simple program to output a pattern on the port. If this doesn't work, post it. Should be no longer than perhaps 20 lines.

That you have nothing, suggests you have something fundamentally 'wrong'.

[nailuy]

Thank you again Ttelmah
now I make mini test program:

Compiler is : PCWHD 4.140

[Ttelmah]

Start by actually putting the bit_test instructions....

But simple questions:
Have you verified the chip is running at all?. Has it got a 20Mhz crystal on the OSC1/OSC2 pins?. Is MCLR pulled up?.

[nailuy]

Yes
MCLR I have 4.6V
And frequency is 4Mhz so I changed.
Problem still persist.
What I can do next?

[Ttelmah]

As I said, start by putting the bit test instructions.

Look what I posted, and what you have done. They are radically different....

[nailuy]

What do you mean on Bit test instruction.
you want to put .LST file?
I read your post from up but I'm not understanding.
you want to put only this command :

[PCM programmer]

He means that you left out all the bit_test function names in your first
posted code. He means put the bit_test function name into your code,
as you did below (in bold):

[nailuy]

"bit_test" is function in help mode I understand what is doing.
now I tested this:

[alan]

As asked, have you verified that your processor are indeed running by using the blink LED test.

Regards

[nailuy]