Execution and Reading from parallel EEPROM

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Hi,

 I am working with parallel EEPROM and the application is as follows:

The code will be executed from parallel EEPROM and i require to read
total contents of the same parallel EEPROM, Which i am unable to read.

Is it possible in EEPROM to read the when executing from the
same(EEPROM)?

I am using AT28HC256 EEPROM.

Pls let me know the information on the above at the earliest.


Thanks in advance,
Amul

Re: Execution and Reading from parallel EEPROM

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Unable why?  How exactly did you try to do it?  What's preventing you
from succeeding to do it?

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Depends on what CPU you're using.  If it's a von-Neumann architecture,
it should know how to disentangle code fetches and data memory access
properly.  If you've von-Neumann'ed a Harvard architecture processor
by means of external chip select logic, you *might* be in trouble.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: Execution and Reading from parallel EEPROM
Hi,
You have to copy your code in RAM (code which read or write in EEPROM) and
execute it in RAM. After these operations, you can return in your EEPROM
code.
Yvan

**********************
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  http://www.ybdesign.fr
**********************

message : blrjdg$o1e$ snipped-for-privacy@nets3.rz.RWTH-Aachen.DE...
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Re: Execution and Reading from parallel EEPROM
Depends on CPU/controller used. Please specify.
I think you mean writing AND excecuting code of the EEPROM at the same time.
This is not possible. The EEPROM is locked until write has taken.
- Henry

Ammulu schrieb in Nachricht
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Re: Execution and Reading from parallel EEPROM
reddy snipped-for-privacy@yahoo.com (Ammulu) wrote in message
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If you can execute code from a 28HC256 EEPROM you *are* reading it.
Perhaps your processor is configured to treat the device as
CODE-memory only, using another memory-space (or chip-select) for DATA
memory.
Wade

Re: Execution and Reading from parallel EEPROM
Hi,

I am using Motorola 68332 Microcontroller(basically CPU32 arch).

I need execution and reading from same EEPROM.

When I am executing the same code from RAM, i am able to read entire
EEPROM  to calculate the CHECKSUM of the same code.

I am not able to read the entire EEPROM when executing the code from
EEPROM, it should be noted that the code being executed is also to be
read for my purpose.

pls give more information for the above



 Thanks in advance,
 Amul

Re: Execution and Reading from parallel EEPROM

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How does it show that you're not able to read the EEPROM data?

Are you sure that there are no locations written in the middle of the code?
The data of the code can be in the same meory block if the code is run from
RAM, but the data must be located to the RAM separate from the EEPROM when
running code from the EEPROM - you *cannot* use the same piece of binary
code. Check your linker map.

Been there - done that (with a 68332) - it does work properly done.

HTH

Tauno Voipio
tauno voipio @ iki fi




Re: Execution and Reading from parallel EEPROM
reddy snipped-for-privacy@yahoo.com (Ammulu) wrote in message
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You say you can boot up but not read the entire EEPROM(?)
The default size of the boot-ROM chip-select is 2Kbytes; to address a
28HC256 you must change the size to at least 8Kbytes

 Another possibility: you _may_ have the CPU configured for separate
data/code spaces: check the reset-time setup (certain data lines are
pulled down by reset to configure the operation.)

Also: are the wait-state settings correct? Parallel EEPROMs are slow.

(This is based on experience with the 68HC16, which has the same
peripheral interface as the 68332.)

Good luck. It'll be fun once you get past the bumps
Wade Hassler

Re: Execution and Reading from parallel EEPROM
Hi,

  I am writing data to parallel EEPROM through programming tool right now.

  Is it possible to write parallel EEPROM through software ?
 
  If possible, is it through alogrithm or through proper timing of control
signals ?

I could find alogrithm for chip erase of parallel EEPROM .


HTH,

Amul.

Re: Execution and Reading from parallel EEPROM

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signals ?
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Get the data sheet of the EEPROM chip you're having. It tells how.

Tauno Voipio
tauno voipio @ iki fi




Re: Execution and Reading from parallel EEPROM
Hi,
Yes, you can write to tour EEPROM through your embeded software, but the
function to do this MUST be executed in RAM.
There's no algorithm to write in EEPROM (28Cxx I think...), it's like an RAM
write, but the difererence is a delay after the WR pulse before an athoer
access to the EEPROM. This delay is the time that the EEPROM spend to write
the byte inside its memory array (have a look at "DATA polling" and "Toggle
bit" in the datasheet).
So, there is no algorithm for these type of memory (except to lock and
unlock "software data protection").

Yvan

**********************
            YBDesign
  http://www.ybdesign.fr
**********************

snipped-for-privacy@posting.google.com...
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signals ?
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Re: Execution and Reading from parallel EEPROM

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Not necessarily.  It just must be executed _somewhere_ else than the
EEPROM you're writing to.  Could be anything, really.  RAM, a
boot-loader PROM, CPU-internal code memory if your chip has any, or
just a second EEPROM.  

If the micro in question is a Harvard architecture, wiring a
von-Neumann RAM section just for this might be a waste of effort, and
one of the other methods would work better.
--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

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