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'[PIC] Migrate from PIC16F877 to PIC16F877A'
2006\06\04@215822 by Charles Oram

picon face
Hi,
Has anyone out there had problems migrating form the PIC16F877 to the
PIC16F877A, particularly in the areas of the oscillator and MCLR pin? I've
noticed from the datasheets, migration document and searching on the 'net
that these could be problem areas. The circuit I have pulls MCLR up with a
100k resistor (most seem to use a 10k).
I don't know if I will have a problem and I know that the real answer is
"try
it and see", but I have a customer who needs to build 80 units and can't get
'877s, so they want to build them with the '877A and have me fix the
software to work later.

regards,
Charles

_________________________________________________________________
Check out the latest video  @  http://xtra.co.nz/streaming

2006\06\05@060855 by Bob Axtell

face picon face
Charles Oram wrote:
> Hi,
> Has anyone out there had problems migrating form the PIC16F877 to the
> PIC16F877A, particularly in the areas of the oscillator and MCLR pin? I've
> noticed from the datasheets, migration document and searching on the 'net
> that these could be problem areas. The circuit I have pulls MCLR up with a
> 100k resistor (most seem to use a 10k).
>  
100K is far outside the value expected by the ICD2 and most programmers.
27K is the highest value I
would recommend. 10K is what Microchip recommends, but I think it is too
low.
> I don't know if I will have a problem and I know that the real answer is
> "try
> it and see", but I have a customer who needs to build 80 units and can't get
> '877s, so they want to build them with the '877A and have me fix the
> software to work later.
>  
That resistor is probably your main problem.

> regards,
> Charles
>
> _________________________________________________________________
> Check out the latest video  @  http://xtra.co.nz/streaming
>
>  

2006\06\05@084301 by William Bross

picon face
Charles Oram wrote:

>Hi,
>Has anyone out there had problems migrating form the PIC16F877 to the
>PIC16F877A, particularly in the areas of the oscillator and MCLR pin? I've
>noticed from the datasheets, migration document and searching on the 'net
>that these could be problem areas. The circuit I have pulls MCLR up with a
>100k resistor (most seem to use a 10k).
>I don't know if I will have a problem and I know that the real answer is
>"try
>it and see", but I have a customer who needs to build 80 units and can't get
>'877s, so they want to build them with the '877A and have me fix the
>software to work later.
>
>regards,
>Charles
>
>_________________________________________________________________
>Check out the latest video  @  http://xtra.co.nz/streaming
>
>  
>
Physically...never had a problem.   Check for differences in the
configuration though.  Here is part of my standard header:
(watch out for line wrap)
#ifdef    PROD
#ifdef    ICE2000
   #include <p16f877.inc>        ; processor specific variable definitions
   __CONFIG _CP_OFF & _WDT_ON & _BODEN_ON & _PWRTE_ON & _HS_OSC &
_WRT_ENABLE_OFF & _LVP_OFF & _DEBUG_OFF & _CPD_OFF
#endif
#ifndef    ICE2000  
   #include    <p16f877A.inc>    ; processor specific variable definitions
   __CONFIG _CP_ALL & _WDT_ON & _BODEN_ON & _PWRTE_ON & _HS_OSC &
_WRT_OFF & _LVP_OFF & _CPD_OFF

#endif
#endif

Bill

2006\06\05@104206 by Xiaofan Chen

face picon face
On 6/5/06, Bob Axtell <spam_OUTengineerTakeThisOuTspamcotse.net> wrote:
> Charles Oram wrote:
> > Hi,
> > Has anyone out there had problems migrating form the PIC16F877 to the
> > PIC16F877A, particularly in the areas of the oscillator and MCLR pin? I've
> > noticed from the datasheets, migration document and searching on the 'net
> > that these could be problem areas. The circuit I have pulls MCLR up with a
> > 100k resistor (most seem to use a 10k).
> >
> 100K is far outside the value expected by the ICD2 and most programmers.
> 27K is the highest value I  would recommend. 10K is what Microchip
> recommends, but I think it is too low.

Other than this problem, there is a migration document which may be
of some help.
http://ww1.microchip.com/downloads/en/DeviceDoc/39591a.pdf

Regards,
Xiaofan

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