Data EEPROM of PIC questions - Page 3 - Electronic Circuits Projects Diagrams Free

bananasiong · 25th July 2007, 08:31 AM

Quote:

Originally Posted by Pommie

The main difference between flash and EEPROM is the number of times you can write to it. Flash may fail after only 1000 writes, EEPROM is guaranteed for 10,000 writes but will typically last 1,000,000 writes.

EEPROM should be used to store things that may change infrequently such as customer preferences.

Flash should contain data that changes very infrequently such as the program code (changed when a bug is fixed or the code updated). You can also use flash to store data. For example, a musical doorbell may have the code and a tune programmed when it is manufactured but different tunes could be made available via the internet that could be flashed into the memory via RS232.

Mike.

So ideally speaking, we write to the flash everytime we program the chip? And the chip is unusable after 1000 times programming.
If my program occupy for only 1 page, 0x0000 to 0x07ff, I can only store additional data into the second page right?

Hi Gayan, I know what EEPROM is, I'm using it to store the time of my clock

Pommie · 25th July 2007, 08:43 AM

You can store code or data in page two.

1000 writes for flash is the worst case - it is typically 100,000.

You seem to keep asking the same questions again and again. If you still have questions you should read the section "PCL and PCLATH" in the data sheet - normally section 2.2

Mike.

**Nigel Goodwin** · 25th July 2007, 08:45 AM

Quote:

Originally Posted by bananasiong

So ideally speaking, we write to the flash everytime we program the chip? And the chip is unusable after 1000 times programming.

No, it's guaranteed to have a minimum life of 1000 times, in reality it will almost certainly have a much longer life.

Quote:

If my program occupy for only 1 page, 0x0000 to 0x07ff, I can only store additional data into the second page right?

No - the entire 2K is program memory, I strongly suggest you use it as such and forget about writing directly to program memory - it's NEVER a good idea to write code that modifys program memory - unless you have a seriously good reason (such as a bootloader).

Pommie · 25th July 2007, 08:58 AM

Quote:

Originally Posted by Nigel Goodwin

it's NEVER a good idea to write code that modifys program memory - unless you have a seriously good reason (such as a bootloader).

Why? Storing things like,
Customer address for anti theft purposes,
Mapping tables for CDI,
String tables for different languages,
Are all reasons to write to the code area. Why do you think microchip gave you the ability to read and write to this area?

Most cars, mobile phones, network hubs, motherboards and even my DVD recorder are flash upgradable.

Mike.

bananasiong · 25th July 2007, 09:14 AM

Quote:

Originally Posted by Pommie

You can store code or data in page two.

1000 writes for flash is the worst case - it is typically 100,000.

You seem to keep asking the same questions again and again. If you still have questions you should read the section "PCL and PCLATH" in the data sheet - normally section 2.2

Mike.

It is because I didn't know what's the point of writing into the program memory. I thought that write the program into the program memory and I couldn't figure out why is it needed because the program is already there.
Now I know that the reading from and writing to the flash program memory section in the datasheet is refering to the data, but not the instructions.

**Nigel Goodwin** · 25th July 2007, 09:24 AM

Quote:

Originally Posted by bananasiong

It is because I didn't know what's the point of writing into the program memory. I thought that write the program into the program memory and I couldn't figure out why is it needed because the program is already there.

You're just confusing yourself, ignore that capability, or choose a PIC that doesn't include it (it's a relatively 'recent' addition) - it's rare to require it, and you almost certainly don't!.

As Pommie says, there are occasions where it's useful, although many of the applications (and the most important ones) he listed are just using it as a bootloader to reprogram the device.

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25th July 2007, 08:43 AM	(permalink)
Pommie	You can store code or data in page two. 1000 writes for flash is the worst case - it is typically 100,000. You seem to keep asking the same questions again and again. If you still have questions you should read the section "PCL and PCLATH" in the data sheet - normally section 2.2 Mike.