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'Re[2]: pic questions'
1998\06\29@180010 by Martin Green

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    Someone wrote:

> Im confused by the plethora of chips available and after
>studying
>their selector guides and looking in catalogs, I still have some
>questions. Some eeprom pics are "flash" and others just eeprom. Whats
>the dif? 16c84 versus 16f84?

    Which was answered with:

The name mostly.  The 16C84 is pretty much discontinued, having been
replaced by the 16F84.  Both have EEPROM type program memory, which to
the user means it can be reprogrammed without needing to erase the chip
with UV light.  In the process of loading a new program, the chip
automatically erases the old one.  Buy 16F84's if your programmer can
program them (nearly all do).

    Where did you hear that the 16C84 has been discontinued? Microchip has
    repeatedly stated that the 'C' will NOT be discontinued, and that they
    are committed to producing older chips for a long time to come. The
    'F' has twice the RAM, twice the EEPROM (I think - haven't used it
    yet) and a few other minor enhancements. Because it uses FLASH for
    program memory and not EEPROM, it is cheaper. This economy along with
    the increased feature list makes it more attractive than the 'C', but
    the 'C' will be with us for some time yet.


    CIAO - Martin.


    BTW - FLASH and EEPROM are similar, but as I understand it, it takes
    less transistors to make a FLASH cell, hence thay are cheaper per byte
    than EEPROM. Other than that, don't worry too much about the
    difference, your 16C84 programmer should work fine with the 'F84.

1998\06\29@195011 by Mike Keitz

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On Mon, 29 Jun 1998 15:25:15 -0400 Martin Green
<spam_OUTMartin_GreenTakeThisOuTspamCONSUMERSGAS.COM> writes:
>>Whats
>>the dif? 16c84 versus 16f84?
>
>     Which was answered with:
>
>The name mostly.  The 16C84 is pretty much discontinued, having been
>replaced by the 16F84.  Both have EEPROM type program memory, which to
>the user means it can be reprogrammed without needing to erase the
>chip
>with UV light.  In the process of loading a new program, the chip
>automatically erases the old one.  Buy 16F84's if your programmer can
>program them (nearly all do).
>
>     Where did you hear that the 16C84 has been discontinued?

A while ago, several list members said they were having trouble finding
16C84 parts, and distributors were saying that Microchip had discontinued
them.  I would think the C84 is at least in a "not recommended for new
design" classification.

>Microchip has
>     repeatedly stated that the 'C' will NOT be discontinued, and that
>they
>     are committed to producing older chips for a long time to come.

This is probably true.  The old 16C5x's are still made, though now cost
more than some of the the low-end 14-bit parts that could do the same
function.

>The
>     'F' has twice the RAM, twice the EEPROM (I think - haven't used
>it
>     yet)

Nope.  Here are the memory sizes:

Type    C84     F84
RAM     36      68
EEPROM  64      64
Program 1024    1024

> and a few other minor enhancements.

Better code protection and lower standby power I think are the only other
user-noticeable differences.

> Because it uses FLASH
>for
>     program memory and not EEPROM, it is cheaper.

Flash does indeed pack a lot of bits into small space and cost.  If
Microchip did use it, I would think that a "flash" part with more than
1024 program would be made (It would be very popular).  This is just
conjecture, but it appears that the program memory in the F84 is the same
EEPROM technology as in the C84, thus the program size was not increased.

Since I really don't know (or care) how the chip works internally, it's
just a guess.   Microchip did sort of confirm it by claiming in "The
Truth about AVR" that a F84 program could be modified one location at a
time without erasing the whole chip.  Sounds like EEPROM to me.  Of
course everything in that infamous document wasn't exactly true.

This economy along
>with
>     the increased feature list makes it more attractive than the 'C',
>but
>     the 'C' will be with us for some time yet.

I think Microchip bumped up the price of the C84 a little to encourage
people to buy the F84 instead.  There's really no reason to buy C84
instead of F84 parts unless your programmer won't handle them.  Even then
you can get by if you don't try to enable the code protection and
remember that the power-up timer control fuse works opposite that of the
C84.

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1998\06\29@212606 by myke predko

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On the 16C84 availability Martin Green wrote:

>The name mostly.  The 16C84 is pretty much discontinued, having been
>replaced by the 16F84.  Both have EEPROM type program memory, which to
>the user means it can be reprogrammed without needing to erase the chip
>with UV light.  In the process of loading a new program, the chip
>automatically erases the old one.  Buy 16F84's if your programmer can
>program them (nearly all do).
>
>     Where did you hear that the 16C84 has been discontinued? Microchip has
>     repeatedly stated that the 'C' will NOT be discontinued, and that they
>     are committed to producing older chips for a long time to come. The
>     'F' has twice the RAM, twice the EEPROM (I think - haven't used it
>     yet) and a few other minor enhancements. Because it uses FLASH for
>     program memory and not EEPROM, it is cheaper. This economy along with
>     the increased feature list makes it more attractive than the 'C', but
>     the 'C' will be with us for some time yet.

Martin, last year at this time, Microchip did say they had obsoleted the
16C84 and would no longer produce it.  I know this from painful memory
because I had to go through all the experiments in my book over a week last
July and make sure they would work on the 16F84 (I had originally written
them for 16C84).

Maybe Darrell could update us on the current state of the 16C84?

>     BTW - FLASH and EEPROM are similar, but as I understand it, it takes
>     less transistors to make a FLASH cell, hence thay are cheaper per byte
>     than EEPROM. Other than that, don't worry too much about the
>     difference, your 16C84 programmer should work fine with the 'F84.

Yes, it takes fewer transistors, but true Flash is harder to manufacture
than EEPROM because the control gate (which transfers the charge to the
floating gate) has to be made much more precisely (ie the charge can pass
from the gate, into the substrate and affect other circuits).

myke

This week in myke's Book Room: Houdini, biographies and his writings.

http://www.myke.com/Book_Room

1998\06\30@133553 by chris

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> Flash does indeed pack a lot of bits into small space and cost.  If
> Microchip did use it, I would think that a "flash" part with more than
> 1024 program would be made (It would be very popular).  This is just
> conjecture, but it appears that the program memory in the F84 is the same
> EEPROM technology as in the C84, thus the program size was not increased.

>From what I've been told by Microchip, the F84 is using similiar
EEPROM technology as the C84.  Not too much of a change here except
for the extra RAM and the inversion of the PWRTE configuration bit.

{Quote hidden}

Microchip still makes (or at least is distributing) the older parts.
The C84 is not recommended for new designs.  Use the F84, it's
cheaper too!

Chris

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