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'[PIC] CCP on dsPIC30 versus 18F - query'
2006\01\18@165434 by John Nall

picon face
I have looked at this until I am blue in the face, and there is
something which I just am not getting!  I would be grateful for a terse
(or extended, as you wish) explanation.

So far as I can tell, prior to the dsPIC family, pics such as the 18F452
(the one I am currently dealing with) had a CCP module, or possibly more
than one.  The CCP module could do either a capture input, or a compare
output.  (They could also do a PWM output, but I'm not dealing with that).

OK, so far so good.  But on the dsPIC30F they changed it to two modules
-- an "input capture module," and an "output compare module."  Why?  
This seems to be to be going backwards, but I'm sure that I'm just not
understanding something.

(As you might figure out, I'm trying to move some code from the 452 to
the 3013).

John

2006\01\18@174905 by olin piclist

face picon face
John Nall wrote:
> OK, so far so good.  But on the dsPIC30F they changed it to two
> modules
> -- an "input capture module," and an "output compare module."  Why?

I can't say why, but they are really unrelated functions if you think about
it.  A better question is why were they in one module in the first place.
The answer to that is probably to reuse the CCP registers.

The dsPICs have two types of PWM generators, "output compare" and motor
control.  I agree that "output compare" is a strange name for something that
is primarily a PWM generator, but once you get past that they are easy to
use and seem to work very well.

> (As you might figure out, I'm trying to move some code from the 452 to
> the 3013).

the 30F4011 would be closer to the 18F452 in pins, program space, and A/D
bits.  The 30F3013 is a great little chip if 8K instructions and 28 pins is
enough.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\01\18@182219 by John Nall

picon face
Olin Lathrop wrote:
> > I can't say why, but they are really unrelated functions if you think about
> it.  A better question is why were they in one module in the first place.
>
>  
.
Well . . . yeah . . . having them as two separate modules is better, I
agree, and they should have done it that way in the first place.  But
they didn't, and to make a radical change now just for the sake of
elegance seems a bit strange.  Perhaps they just figure that migrating
code up to the new generation (I'm kind of lumping the dsPIC chips
together with the 24's and the 33's) is going to be a job, and a little
bit more work for the CCP code is not going to make any big difference.  
If that is the way they look at it, then I applaud.  But it is unusual
for a vendor to do that, IMHO.  They usually stick with the old way,
whether it is the best way or not.  (I know of 1401 emulators running on
IBM mainframes long after most people have no earthly idea what a 1401
is -- and the original 1401 code was emulating a 407 accounting machine
to start with!!  :-)
.
> > the 30F4011 would be closer to the 18F452 in pins, program space, and A/D
> bits.  
.
I agree, but unfortunately I am limited to 28 pins for  this particular
application, because of the circuit board, and the 4011 does not come in
a 28-pin package.  :-(  

John

2006\01\18@183555 by John Ferrell

face picon face
Soon going to ebay...
http://dixienc.us/IBM1401Course.htm

John Ferrell    
http://DixieNC.US

----- Original Message -----
From: "John Nall" <spam_OUTjwnallTakeThisOuTspamgmail.com>
They usually stick with the old way,
> whether it is the best way or not.  (I know of 1401 emulators running on
> IBM mainframes long after most people have no earthly idea what a 1401
> is -- and the original 1401 code was emulating a 407 accounting machine
> to start with!!  :-)
> --

2006\01\18@185301 by olin piclist
face picon face
John Nall wrote:
> I agree, but unfortunately I am limited to 28 pins for  this
> particular application, because of the circuit board, and the 4011
> does not come in a 28-pin package.  :-(

If you're tight on program memory, the 30F4012 might be a good choice if you
only need 10 bit A/Ds (as the 18F452 had).


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\01\18@200134 by John Nall

picon face
John Ferrell wrote:
> > Soon going to ebay...
> http://dixienc.us/IBM1401Course.htm
>  
.
It may be that you and I are the last two people in the entire universe
who have ever heard of  the "set wordmark" command, huh?  :-)


2006\01\19@170456 by Dennis J. Murray

picon face
NOPE - you guys aren't alone!!!!!!!!!!!!!!!

I know this is OT, but I HAD to get my 2 cents in!

I started as a full-time programmer in March, 1964 on a 4K 1401. Moved
up to the big boy - a 16K 1401 and wondered how I'd use all that
memory!! Got to a 709, then a 7090, then a 7094 and thought I'd died &
gone to heaven!

Even went to the IBM announcement of the IBM360 (and later, the 370) -
how many of you youngsters can say that???

I feel that PIC programming in assembly is a LOT easier than a 1401,
where you had only 3 DECIMAL (yes, pre hex) digits to represent up to
16K memory (using zone "punches" over the units & hundreds digits). Got
to be a royal pain.

I, too, don't particularly like banking on the smaller PICs - but even
the mainframes like the 360 and 370 had banking issues - especially if
you were a systems programmer working on large assembly programs (i.e.
portions of the OS).

That's all I'm gonna say - making me feel ancient!
Dennis

John Nall wrote:

{Quote hidden}

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