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'[PIC]: EEPROM <-> PIC'
2002\02\23@051252 by NDuckworth

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Hi Mohit,

From what you've said it sounds like the unknown variable is the size of you
code.
If you have access to a C compiler then I'd suggest making a start on the
program to get a feel for how much space you'll need, you might be pleasantly
surprised.

If you do exceed 8K then a least you'll know more accurately what your
requirements are. Have you looked at the PIC17C756 & 766? They're not Flash but
they would give you 16K to play with and they're available now.

I have no experience of using EEPROM to hold program code but it sounds messy.

Good luck.

Nigel


On Friday, February 22, 2002 12:09 PM, Mohit Mahajan [SMTP:spam_OUTm0h1tTakeThisOuTspamYAHOO.CO.IN]
wrote:
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2002\02\23@140543 by Spehro Pefhany

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At 10:14 AM 2/23/02 +0000, you wrote:

>I have no experience of using EEPROM to hold program code but it sounds messy.

I've done a tokenized custom language that was interpreted by a program in a
micro. The data was stored in a SEEPROM, SPI type for fast access, and
interpreted by runtime code. Kind of like a Basic Stamp but totally
different application-specific language. Really three or four projects-
design the language, write the compiler (in Borland C), write the interpreter
(in assembler), and finally write the program (in the custom language) to
do the job. It took about 2 months total, plus the hardware design and system
design.

I'd suggest staying with the PIC only as long as you are comfortably (no more
than 75% or so) within the memory size (to leave room for the inevitable
feature creep and changes). Don't forget that 8K on a PIC is about 14K bytes.
If you really need more like 32K than 16-18K, I'd suggest the 8051 series
that has lots of memory and is reasonably priced. Or the MSP430 (60K, 16bits)
for a reasonable price. The PIC17C756a has 16k words (28K bytes) of memory,
and lots of I/O, but is OTP only. It's a useful micro, nice and fast. A bit
expensive, and you need a socket adapter to program it with a Picstart+.

BTW, if a lot of your memory is actually strings for display, storing those
in EEPROM is not a bad idea. You could also use it as a way of making the
display language easily changeable. But, be sure to take extra extra extra
precautions in any of these cases to make sure the data is secure in your
EEPROM. You don't want factory returns because of something silly like that.

The amount of controller you're talking about would probably take less than
8K bytes of assembler code, but HLL might stretch it to 8K words, plus
if you have a lot of alphanumeric display strings, it might be a lot more.
Just guesses (but based on quite a few years of designing industrial
instrumentation).

Best regards,






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Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2002\02\23@181245 by Olin Lathrop

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> The PIC17C756a has 16k words (28K bytes) of memory,
> and lots of I/O, but is OTP only.

No, like most PICs that aren't flash, it's available in UV erasable versions
for development.  I've done at least two projects with these that I can
remember and have about 12 of the JW parts left.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, .....olinKILLspamspam.....embedinc.com, http://www.embedinc.com

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