[PIC] Chip Speeds?

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Hi,

Why is it that lots of electronics retailers sell 4mhz pic micros? They
often call then names like..

PIC16F877 04/P

But Microchip list all parts as being 20mhz and dont even bother including
that parameter in the part number? like so...

PIC16F877A-I/P

Are the retailers selling deleted products? or are they just telling fibs?


Thanks

DaveC

Re: [PIC] Chip Speeds?
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I'm not sure where you are reading that they "don't even bother" but the
(maximum) speeds ARE printed on the chips themselves.  I have a 16F877-20/P
right next to me.  The datasheet section on labelling the 16F877 shows the
speed rating in the part number as well.

Random aside:  The 16F877 and 16F877A are slightly different chips.

--
Ben Jackson
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Re: [PIC] Chip Speeds?
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The PIC16F877 04/P is a msot of valid part number.  It is the 4MHz
version of the PIC16F877 in a plastic DIP.  There should be at least
another letter telling you the temperature grade.  There is also a
20MHz version available.

The PIC16F877A-I/P is also a valid part number.  It is the "A"
revision of the PIC16F877.  There is only one speed grade available,
20MHz.  This one is "I"ndustrial temperature and DIP.  From memory, I
think it is 40 pins, 600mil wide but I could be wrong.

Go to Microchip's web site and you can read the revised data sheet and
find out the differences between the chips.

I believe both parts are in production but the PIC16F877A is newer and
probably recommended for new designs.  In nearly all cases you can
transition from the older silicon to the newer.  Sometimes there are
small differences that require code or hardware changes.  Read the
data sheets and errata on Microchip's web site.

Re: [PIC] Chip Speeds?

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Dont' forget that for a 20 MHz PIC, the actual instruction rate is 1/4 that:
5 MHz.

Leon
--
Leon Heller, G1HSM
leon snipped-for-privacy@hotmail.com
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Re: [PIC] Chip Speeds?
On Mon, 07 Jul 2003 06:25:13 GMT, the renowned DaveC

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The PIC16F877 is a different chip from the PIC16F877A. Probably the
former comes in speed grades and the second one doesn't, I've not
looked.

Microchip don't automatically cancel the old version when a new one
comes out, they continue to supply it (usually it costs more, so there
is some incentive to convert) as long as there is enough demand for
their processes.  

You have to pay attention to the differences- which include analog
type issues, programming algorithms and similar stuff. You can't just
automatically sub an A part for the previous part.

Best regards,
Spehro Pefhany
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