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'[PIC]: High Baud Rate on 16F87x'
2002\10\29@223645 by Donovan Parks

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Hello,

I have an application that would benefit for using a high baud rate.  I've
tested the PIC16F876 at 115200bps and it works great!  What I'm wondering is
if I can move upto 230400bps if I use a 18.432MHz crystal.  With this
crystal speed there is 0% error at 230400bps.  My question is if there is a
limitation in the PIC hardware that would prevent this.  I would assume it
would be fine except the 16F87x datasheet doesn't give values for baud rates
over 57600bps.  Frankly, I was a little suprised 115200bps worked.  Thanks.

Donovan

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2002\10\29@231548 by Herbert Graf

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> I have an application that would benefit for using a high baud rate.  I've
> tested the PIC16F876 at 115200bps and it works great!  What I'm
> wondering is
> if I can move upto 230400bps if I use a 18.432MHz crystal.  With this
> crystal speed there is 0% error at 230400bps.  My question is if
> there is a
> limitation in the PIC hardware that would prevent this.  I would assume it
> would be fine except the 16F87x datasheet doesn't give values for
> baud rates
> over 57600bps.  Frankly, I was a little suprised 115200bps
> worked.  Thanks.

       The spec sheets are there only for convinience, the PIC will work at
whatever baud rate you choose to program in the registers. I'm pretty sure
230k would work fine. TTYL

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2002\10\30@042613 by Claudio Tagliola

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I've succesfully tested at 250k and 500k on a 20Mhz PIC. On 1M I got into
trouble becuase my interrupt routine was too slow :)) I have a deployed
application running at 115k2 on the same 20 Mhz crystal, with it's
counterpart being a 40Mhz AMD186. It's a very short line, so that sure
helps, but long-term testing revealed no problems. For what I know, the only
limit is the baudrate divider and the speed of your software to handle
things.

Regards,
Claudio

-----Oorspronkelijk bericht-----
I have an application that would benefit for using a high baud rate.  I've
tested the PIC16F876 at 115200bps and it works great!  What I'm wondering is
if I can move upto 230400bps if I use a 18.432MHz crystal.  With this
crystal speed there is 0% error at 230400bps.  My question is if there is a
limitation in the PIC hardware that would prevent this.  I would assume it
would be fine except the 16F87x datasheet doesn't give values for baud rates
over 57600bps.  Frankly, I was a little suprised 115200bps worked.  Thanks.

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2002\10\30@164526 by Olin Lathrop

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> I have an application that would benefit for using a high baud rate.
I've
> tested the PIC16F876 at 115200bps and it works great!  What I'm
wondering is
> if I can move upto 230400bps if I use a 18.432MHz crystal.

Assuming you calculated the divider value correctly (I didn't check), the
PIC should work fine.  However, note that the common RS-232 converter
chips like the MAX232 only promise to work up to 120Kbaud.

> With this
> crystal speed there is 0% error at 230400bps.  My question is if there
is a
> limitation in the PIC hardware that would prevent this.

Not that I know of.

> I would assume it
> would be fine except the 16F87x datasheet doesn't give values for baud
rates
> over 57600bps.

Those are just quick and dirty numbers for people that are bad at math.  I
would always verify the result anyway.

See my UART_BAUD macro in STD.INS.ASPIC at http://www.embedinc.com/pic.
You give it your clock frequency and desired baud rate, and it calculates
and the UART setup register values for you.  It also bombs out on error if
the desired baud rate can't be achieved within 2.9%.

> Frankly, I was a little suprised 115200bps worked.

I have used 115.2Kbaud on many projects and never had a problem.  I use
that baud rate unless there is some overriding reason not to (very rare).


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2002\10\30@215415 by Donovan Parks

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Thanks for the help.  Glad to hear that it can be done and has be done.

Donovan


> > I have an application that would benefit for using a high baud rate.
I've
> > tested the PIC16F876 at 115200bps and it works great!  What I'm
> > wondering is
> > if I can move upto 230400bps if I use a 18.432MHz crystal.  With this
> > crystal speed there is 0% error at 230400bps.  My question is if
> > there is a
> > limitation in the PIC hardware that would prevent this.  I would assume
it
> > would be fine except the 16F87x datasheet doesn't give values for
> > baud rates
> > over 57600bps.  Frankly, I was a little suprised 115200bps
> > worked.  Thanks.
>
>         The spec sheets are there only for convinience, the PIC will work
at
> whatever baud rate you choose to program in the registers. I'm pretty sure
> 230k would work fine. TTYL
>
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>
>
>

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