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'Easy '877 EEPROM question...'
2000\04\08@020831 by Mike Morris

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<x-flowed>Hi,

I'd just like a confirmation on what I've gleaned from Microchip's somewhat
sparse notes in the datasheet regarding eeprom writes. Am I correct in
assuming that a write to *data* eeprom is basically asyncronous to code
execution, and after following their sequence to initiate a write, I can go
about doing other things, and will be interrupted when the write is complete?

Thanks... (told you it was an easy ques!)

- Mike

</x-flowed>

2000\04\08@065212 by paulb

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Mike Morris wrote:

> Am I correct in assuming that a write to *data* eeprom is basically
> asyncronous to code execution, and after following their sequence to
> initiate a write, I can go about doing other things,

 Definitely.  At least, I speak for the 16F94 which I gather is the
same.

> and will be interrupted when the write is complete?

 Only if you've set up an interrupt.  And doing so is usually
unnecessary complication and obfuscation.  It is generally sufficient to
do something for a while, then *poll* to see whether the write is
finished, else do something else etc...

 Generally speaking:

 While(data_to_be_written)
   { While(EEPROM_BUSY) do { something useful };
     Write_EEPROM;
     do_something_else_useful; }
--
 Cheers,
       Paul B.

2000\04\08@233732 by Jim Robertson

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At 11:05 PM 4/7/00 -0700, you wrote:

Yes, it is asyncronous, you can even do a EEPROM read while the write is in
progress.


Jim

{Quote hidden}

Regards,

Jim Robertson
NEWFOUND ELECTRONICS
________________________________________
Email: spam_OUTnewfoundTakeThisOuTspampipeline.com.au
http://www.new-elect.com
MPLAB compatible PIC programmers.
________________________________________

2000\04\09@061625 by mike

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On Sun, 9 Apr 2000 13:02:57 +1000, you wrote:

>At 11:05 PM 4/7/00 -0700, you wrote:
>
>Yes, it is asyncronous,
True
>you can even do a EEPROM read while the write is in
>progress.
I don't believe this is true. if so it's highly unusual and I'd expect
the data sheet to explicitly state that it is possible - my copy
doesn't.
Of course program memory can be read during the eeprom write cycle.
{Quote hidden}

2000\04\09@202518 by Mike Morris

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<x-flowed>At 11:16 AM 4/9/2000 +0100, you wrote:
> >you can even do a EEPROM read while the write is in
> >progress.
>I don't believe this is true. if so it's highly unusual and I'd expect
>the data sheet to explicitly state that it is possible - my copy
>doesn't.
>Of course program memory can be read during the eeprom write cycle.

If eeprom data memory writes are asyncronous, why would reading eeprom data
memory during a write be prohibited? If it is prohibited, how would it
manifest itself? Return invalid data? Halt execution until the write
completed?  It seems as though if any of those behaviors were true, *that*
would certainly be documented. (One would hope!)

- Mike

{Quote hidden}

</x-flowed>

2000\04\10@060302 by mike

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On Sun, 9 Apr 2000 17:23:02 -0700, you wrote:

>At 11:16 AM 4/9/2000 +0100, you wrote:
>> >you can even do a EEPROM read while the write is in
>> >progress.
>>I don't believe this is true. if so it's highly unusual and I'd expect
>>the data sheet to explicitly state that it is possible - my copy
>>doesn't.
>>Of course program memory can be read during the eeprom write cycle.
>
>If eeprom data memory writes are asyncronous, why would reading eeprom data
>memory during a write be prohibited?
It's reasonable to assume that eeprom array's internal address/data
lines need to be held stable during a write (I don't know if this is
actually the case).
> If it is prohibited, how would it
>manifest itself? Return invalid data?
Possibly, maybe also aborting/corrupting the write
>Halt execution until the write
>completed?  
No - this would add silicon cost
{Quote hidden}

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