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'MPLAB downloads Reply to John Clark'
1999\04\13@184337 by Mail

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HI  John , I am 100% aware of the increase in resolution of  the OSCAL trim
value
on the 12c509A version as there are 5 bits in the oscal or 32 trim levels
assuming
that the Microchip Data sheet 1998 is correct and the sheet 1997 is
incorrect. as shown below

And on the 12c509 there are only 4 bits or 16 trim levels in the oscal reg
my setting on the 12c509 was  B'01100000' , This value is setting the oscal
trim
approx mid way as it ranges from B'0000xxxx' min value to B'1111xxxx'
maximum where x are unimplemented bits ,The reson for me using B'0110xxxx'
on the 12c509 as
it runs the code very close to same speed as if I were using an external XT
resonator
of 4 mhz , leaving enough RESOLUTION left to increase the speed at will.

Now if the same code is moved to a 12c509A with the Oscal setting MAXIMUM
B'11111xxx' then the 12c509A still doesn't run as fast as the 12c509 Which
to my
opinion is running as close as possible to a  4 Mhz resonator on the 12c509
but
on the 12c509A even with the oscal setting maximum it still runs well below
4 mhz  as shown in the test I did below.

Any Suggestions ?  Rewriting the code is NOT an option, only setting the
oscal
value is, As the 12c509 and 12c509A  ARE 100% equivalent ???????? Not to
mention
the higher resolution of OSCAL on the 12C509A?

Regard Mark
spam_OUTjulianTakeThisOuTspamfine.co.za
.....MarkKILLspamspam@spam@fine.co.za


{Quote hidden}

B'11111100'
>> ;which is the maximum speed setting.
>> ;For a 12c509A I would write the Oscal value the same way but
>> ;with differnt value B'11111100' "max speed"
>>
;-------------------------------------------------------------------------
>> -
>> ;(Ocacal register 8Fh) pin definitions as per data sheet 1997 for 12c509A
>>
;-------------------------------------------------------------------------
{Quote hidden}

;-------------------------------------------------------------------------

1999\04\13@224357 by TrionicIan

picon face
> And on the 12c509 there are only 4 bits or 16 trim levels in the oscal reg
>  my setting on the 12c509 was  B'01100000' , This value is setting the oscal
>  trim
>  approx mid way as it ranges from B'0000xxxx' min value to B'1111xxxx'
>  maximum where x are unimplemented bits ,The reson for me using B'0110xxxx'
>  on the 12c509 as
>  it runs the code very close to same speed as if I were using an external XT
>  resonator
>  of 4 mhz , leaving enough RESOLUTION left to increase the speed at will.
>

>From memory so quite likely wrong ...
Is this correct? I thought the oscal had coarse & fine bit settings; so maybe
you were not really setting a mid-value - perhaps you had the coarse setting
at "max", and the improved oscal circuitry does not run as fast.
Can you try a program which determines the ACTUAL execution rate of the
old/new PIC (eg: count to a very big 24bit number then toggle a pin, look at
the pin with a scope)?

Ian C.

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