How to use Assembly in CCS

amit78 · Joined: 17 Jul 2009 Posts: 22 Location: Kolkata, India

Dear All,

In PICMicro Datasheet some times we found some Assembly code snippets. I need to know how should we use those codes in our CCS Program.

For example, currently I am using PIC18F97J60. In the datasheet @page 160, I found one set of assembly code. I like to use that code in my C Code. I went to CCS Help but, may be I am missing something. I need little guidance.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

For your information, the compiler automatically puts the following code at
the start of main():

amit78 · Joined: 17 Jul 2009 Posts: 22 Location: Kolkata, India

Thank you So Much for your Prompt Reply.

I will check it.

newguy · Joined: 24 Jun 2004 Posts: 1924

Both the compiler's built-in help and the manual have entries. Search for #asm. If you really need to include assembly instructions, they're inserted with a starting #asm and ended with #endasm.

Between the manual, help and searching here, you'll be able to figure things out very quickly.

JAM2014 · Joined: 24 Apr 2014 Posts: 140

Hi,

One question I would ask is "why are you doing this"? CCS has built-in high level functions to do the simple initialization/configuration stuff you want/need to do! This is one of the huge benefits of CCS C. In 10+ years of PIC coding with CCS C, I've only used .asm 1 time, and that was to ensure the fastest possible control of some digital I/O with a particularly time-fussy LED driver chip. I'd be really shocked if you *truly* need to use .asm in your projects. Basically, if you are going to use CCS C then use CCS C, which means using the built-in functions and C syntax to do what you need to do!

Jack

temtronic · Posted: Thu Jun 09, 2022 2:41 pm

Agree with Jack ... WHY is ASM needed ?

I've actually only needed ASM TWICE in 25 years, both were custom very time sensitive interfaces to client's hardware.

curious to know...

Jay

dyeatman · Joined: 06 Sep 2003 Posts: 1968 Location: Norman, OK

I designed several real time control systems for large industrial equipment
and, with careful coding and time slicing, did not need ASM at all. I used ASM a
couple of times in earlier versions of CCS to lock/unlock registers but not any
more since they got that fixed.
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PCM programmer · Joined: 06 Sep 2003 Posts: 21708

temtronic,
He wanted ASM because he wanted the init code published in the PIC data
sheet, and he didn't know that CCS automatically puts it at the start of main.
Now he knows.

Humberto · Posted: Fri Jun 10, 2022 9:32 pm

Thanks PCM Programmer for so brilliant answer (one more time).
The CCS compiler has many years of maturation through which it has achieved good code optimization
compared to earlier versions.
It is always a temptation to use Assembler to solve critical situations, but it is often solved by modifying an
algorithm or optimize some hardware issue.

Best wishes
_________________
Humber

Ttelmah · Joined: 11 Mar 2010 Posts: 19967

Yes,
Even this has become less and less necessary.

Historically when the V5 compilers started some code got larger than it
had been on the V4 compilers.
I recently had cause to recompile some old V4 code, and was impressed
to see that now the result was nearly 200 bytes smaller than the V4
version.
On performing basic tasks, with a bit of care in how things are defined
and done it is possible now to pretty much do every assembler operation
in C with the same result, by doing direct accesses as PCM shows.
I've posted things like replacements for the flash memory access routines
(where several compiler versions had problems), that are direct translations
of the assembler posted in the data sheets, into C, and are simple, and
result in exactly the same assembler.

It really has become almost totally unneeded now. Smile