Toggle Port B 16f877

[Peter Mayhew]

I have been writing code in ASM which all works fine, and now writing the same code using CCS, however I'm having trouble with the basics of simply toggling portb output pins.

When I monitor the special function registers portb in debug they do toggle, however when i blow the pic, and probe with the scope, there is no toggling.

Something basic i'm doing wrong, help please?

[horde_fuego]

[andyfraser]

You don't need a delay unless you have really, really slow scope !

You are setting all the pins to INPUT with set_tris_b(0xFF);

HTH

Andy

[Guest]

Hi,

Which is why it's a good idea to just let the compiler handle setting the TRIS settings, especially for a beginner. The only time you need to explicitly specify the TRIS settings yourself is when you use FAST_IO.

Chas

[Peter Mayhew]

Many thanks for all your advice.
Yes my scope is fast enough, thanks for pointing that out.
You are correct, I did have tris_b set to 0xff, which was a silly mistake. That happened as I was originally reading port B and outputting to port A, but when I found the program wasn't working as expected. just toggled port b but forgot to update tris_b to 0x00. Well spotted, thankyou.
I changed tris_b to an output 0x00. However this didn't solve the problem.
I went through a couple of example files and found the code
#fuses HS,NOWDT,NOPROTECT,NOLVP
So I added #fuses HS and the program works.
Complete code

[bungee-]

Peter use the project wizard for starting a new project. One of my favorite function is setting correct fuses, so you allways know how the PIC is set.

[Peter Mayhew]

Funny you should mention that. I did use the menu Project --> Project Wizard. I just checked it again, and can't see any mention of the fuses??? I can only find it in menu configure --> configuration bits? Maybe there is something I missed??

[PCM programmer]

The command line compilers used with MPLAB don't have any
of the CCS Wizards.

[dyeatman]

Peter,
If you had used the "PIC Wizard" that comes with the CCS IDE, under General Category there is an Options Tab. On that tab you will find the Fuses panel on the bottom half of the tab page right below where you set the Oscillator Frequency. This section sets the fuses automatically according to the speed and type of oscillator along with the other options desired. That's the section I believe he was referring to.

Also, Charles is right, you really should avoid using the TRIS() statements unless you absolutely have to. The compiler will set the port bits automatically.

[Peter Mayhew]

I don't know about CCS IDE. My copy of CCS is quite old, which I bought back in 2003. I don't think they had CCS IDE back then?, or you had to avoid using TRIS. All I know is its PCM Software.