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'RAM EXPANSION'
1998\05\04@114750 by eslight

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Anyone here knows if there's a way to adress more ram with
a pic? not for storing data, that I could do it easily by
adding a serial eeprom or whatever, but I mean program memory,
for example if I buy a 16F84, I am stuck with only 1K of eeprom
program memory, is there a way to reroute the port for data/adress
bus? is it easy to do? would I require a 22 or 33 ports chip instead
of a 11? or I am stuck with what I buy and I'd have to check for
a 4 or 8K eprom/otp PIC?



-----------------------------------------------
Eric Slight          E-mail: spam_OUTeslightTakeThisOuTspammatrox.com

DigiSuite SQA Specialist.
Video Production Group, Matrox Electronics Inc.
Dorval, Quebec (Canada).
-----------------------------------------------

1998\05\04@134859 by Andrew Warren

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Eric Slight <.....eslightKILLspamspam@spam@Matrox.COM> wrote:

> if I buy a 16F84, I am stuck with only 1K of eeprom program memory,
> is there a way to reroute the port for data/adress bus?

   No.  If you want an external address/data bus, you'll need to
   use one of the PIC17 family.

   -Andy

=== Andrew Warren - fastfwdspamKILLspamix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499 (personal)
=== http://www.netcom.com/~fastfwd (business)

1998\05\04@165705 by eslight

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> > if I buy a 16F84, I am stuck with only 1K of eeprom program memory,
> > is there a way to reroute the port for data/adress bus?
>
>     No.  If you want an external address/data bus, you'll need to
>     use one of the PIC17 family.

You mean I'll have to buy a bigger romable code chip ?
or you mean there's a chip that you can hook up with the
pic that does the job, or what? :)

I used to do ram expansion when needed with  68hc11 but the
pic doesn't work the same way and I don't know how to adress
pass 3ff with external memory, for example



--
-----------------------------------------------
Eric Slight          E-mail: .....eslightKILLspamspam.....matrox.com

DigiSuite SQA Specialist.
Video Production Group, Matrox Electronics Inc.
Dorval, Quebec (Canada).
-----------------------------------------------

1998\05\04@171855 by Andrew Warren

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Eric Slight <EraseMEeslightspam_OUTspamTakeThisOuTMatrox.COM> wrote:

> > > if I buy a 16F84, I am stuck with only 1K of eeprom program memory,
> > > is there a way to reroute the port for data/adress bus?
> >
> >     No.  If you want an external address/data bus, you'll need to
> >     use one of the PIC17 family.
>
> You mean I'll have to buy a bigger romable code chip ?
> or you mean there's a chip that you can hook up with the
> pic that does the job, or what? :)
>
> I used to do ram expansion when needed with  68hc11 but the pic
> doesn't work the same way and I don't know how to adress pass 3ff
> with external memory, for example

Eric:

None of the 12- and 14-bit PICs (PIC12Cxxx, PIC14xxx, PIC16C5x,
PIC16Cxx, etc.) support external program memory.

The only PICs whose I/O pins can be configured as an external
address/data bus (like the 68HC11 with which you're familiar) are
the 16-bit PICs (PIC17C4x, etc.).

If your code will not fit in your current PIC, you have two choices:

   1.  Buy a PIC with more internal program memory than what you're
       using now, or

   2.  Replace your current PIC with a PIC17Cxx device, configure
       it for either "microprocessor" or "extended microcontroller"
       mode, then add all the external memory (and address-decoding
       and latching logic) that you want.

-Andy

=== Andrew Warren - fastfwdspamspam_OUTix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499 (personal)
=== http://www.netcom.com/~fastfwd (business)

1998\05\05@110936 by eslight
picon face
Ahhh cool, thanks a lot :)

Andrew Warren wrote:
{Quote hidden}

--
-----------------------------------------------
Eric Slight          E-mail: RemoveMEeslightTakeThisOuTspammatrox.com

DigiSuite SQA Specialist.
Video Production Group, Matrox Electronics Inc.
Dorval, Quebec (Canada).
-----------------------------------------------

1998\05\21@214419 by Larry G. Nelson Sr.

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Another approach is to impliment a system like the basic stamp where you
run an interpreter on the chip with external memory holding the code. While
not an ideal solution it would allow you to expand memory at the cost of
speed and a couple of I/O pins.


At 02:16 PM 5/4/98 -0800, you wrote:
{Quote hidden}

Larry G. Nelson Sr.
RemoveMEL.NelsonspamTakeThisOuTieee.org
http://www.ultranet.com/~nr

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