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question on set_tris_x function

 
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arao



Joined: 15 May 2012
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question on set_tris_x function
PostPosted: Tue May 15, 2012 11:06 am     Reply with quote
I see the following in CCS documentation regarding set_tris_x().
SET_TRIS_B( 0x0F );
// B7,B6,B5,B4 are outputs
// B15,B14,B13,B12,B11,B10,B9,B8,B3,B2,B1,B0 are inputs
I’m trying to understand if this is an error in documentation.

If each bit represents a PIN, then ONLY Bits 0-3 are INPUTS and Bits 4-7 are OUTPUTS.

The documentation talks about B15-B8 as inputs as well?? Why?
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Tue May 15, 2012 11:12 am     Reply with quote
You are reading the manual for the PCHD compiler (for PIC's like the PIC24), which perform 16bit I/O by default.
Are you using a PIC24, or a PIC16/PIC18?.
On the latter, the ports are only 8bits wide.

Best Wishes
arao



Joined: 15 May 2012
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question on set_tris_x function
PostPosted: Tue May 15, 2012 1:03 pm     Reply with quote
I am currently using a PIC18F2680. I referred to the document by just clicking on the ? button on the IDE.

Regards.
SherpaDoug



Joined: 07 Sep 2003
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PostPosted: Tue May 15, 2012 2:00 pm     Reply with quote
It does look a little confusing. But the best way to resolve this and similar issues is to compile a trivial program and look at the assembly listing.

Please share the result for the next person with the same problem.
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PCM programmer



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PostPosted: Tue May 15, 2012 2:08 pm     Reply with quote
Quote:

I am currently using a PIC18F2680.

Here is the PDF manual for your compiler. Download it and put it on
your Windows desktop. Look up set_tris_x in this manual:
http://www.ccsinfo.com/downloads/ccs_c_manual.pdf
Ttelmah



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PostPosted: Wed May 16, 2012 2:33 am     Reply with quote
I'm wondering if your IDE has somehow got the PCD manual linked by mistake:
On mine, if working with a 16bit PIC, the manual gives:
Code:

Examples:
 SET_TRIS_B( 0x0F );

   // B7,B6,B5,B4 are outputs

   // B15,B14,B13,B12,B11,B10,B9,B8, B3,B2,B1,B0 are inputs

but if working with a 8bit PIC, gives:
Code:

Examples:
 SET_TRIS_B( 0x0F );

   // B7,B6,B5,B4 are outputs

   // B3,B2,B1,B0 are inputs

Getting the wrong manual, will happen if you initialise the project having selected the PIC24 mode, then switch to using the PIC18 mode. The IDE remembers the manual link for the original selected mode....

Something like this has happened to you. Selecting the manual yourself (either by loading the pdf manual, or by selecting the .chm file directly in the compiler directory), will hopefully give you the right manual.

Best Wishes
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