Data EEPROM of PIC questions - Page 2 - Electronic Circuits Projects Diagrams Free

bananasiong · 23rd July 2007, 08:40 AM

But the notes say that

Quote:

The device programmer can no longer access this memory.

means the EEPROM will not be cleared with bulk erased, can only be erased by writing erase routine in the program?

Pommie · 23rd July 2007, 09:07 AM

The programmer can no longer read or write to the EEPROM. It can however clear it with bulk erase.

Mike.

**Nigel Goodwin** · 23rd July 2007, 09:11 AM

Quote:

Originally Posted by Pommie

The programmer can no longer read or write to the EEPROM. It can however clear it with bulk erase.

Exactly!

bananasiong · 23rd July 2007, 09:45 AM

How about the flash memory in the PIC? Is it another memory that stores the data?

**Nigel Goodwin** · 23rd July 2007, 10:54 AM

Quote:

Originally Posted by bananasiong

How about the flash memory in the PIC? Is it another memory that stores the data?

That's the program memory - read the datasheet!.

bananasiong · 24th July 2007, 01:08 AM

Any clue? The datasheet states only how to read and write into it. I couldn't find any notes from microchip site too.
Does the program memory store the program instructions?

Gayan Soyza · 24th July 2007, 04:36 AM

Program memory stores the program instructions.
Data memory consists of EEPROM and RAM memories.

For Bananasiong this will be helpful.

http://www.mikroe.com/en/books/picbook/2_06chapter.htm

bananasiong · 24th July 2007, 09:14 AM

Still couldn't figure it out. Isn't the program stored in the location start from 0x0000? Then for the flash program memory? To store more program instructions start from the 0x1000?
I'm refering to PIC16F88.

**Nigel Goodwin** · 24th July 2007, 09:53 AM

Page 11, figure 2.1 - shows 4K of program memory from 0x0000 to 0x0FFF - that's it, total program memory. If you try and run the program counter past that end address it loops back to 0x0000 again.

bananasiong · 24th July 2007, 02:54 PM

Quote:

Originally Posted by Nigel Goodwin

Page 11, figure 2.1 - shows 4K of program memory from 0x0000 to 0x0FFF - that's it, total program memory. If you try and run the program counter past that end address it loops back to 0x0000 again.

Hi,
I know about this, 4 k of program memory from 0x0000 to 0x0fff (aka on chip program memory), 2 k for each page and there are two pages.
I just don't know what's the purpose of writing to or reading from the flash. According to the datasheet,

Quote:

The PIC16F87/88 devices have 4K words of program Flash with an address range from 0000h to 0FFFh. Addresses above the range of the respective device will wraparound to the beginning of program
memory.

So flash program memory is also on chip program memory? Why we need to write into our program memory since the program is already there?

Thanks

**Nigel Goodwin** · 24th July 2007, 02:59 PM

Quote:

Originally Posted by bananasiong

So flash program memory is also on chip program memory? Why we need to write into our program memory since the program is already there?

I don't understand what you're asking? - 'program memory' and 'flash memory' are the same thing - you've got 4K of memory that goes from 0x0000 (the reset vector) to 0x0FFF (the end of memory). That's it, your total program memory - nothing else.

Pommie · 24th July 2007, 03:09 PM

You read and write to flash to store/retrieve data. I store messages as 2 x 7 bit ascii characters per location and have filled a 2K bank with text (4000 chars). If you wanted to do a data logger then you can store lots of readings as long as they don't arrive too fast. Bootloaders write code to flash.

One nice thing about the USB enabled pics is the bootloader. The bootloader sits in the first 2K of memory and your program gets sent via USB and is written in the other 30k of flash.

Mike.

bananasiong · 25th July 2007, 12:16 AM

Quote:

Originally Posted by Nigel Goodwin

I don't understand what you're asking? - 'program memory' and 'flash memory' are the same thing - you've got 4K of memory that goes from 0x0000 (the reset vector) to 0x0FFF (the end of memory). That's it, your total program memory - nothing else.

Since it is the program memory, I don't see what's the point of doing this:

Let's say I read from 0x0000, what will I get? Isn't it
goto Initialize (my program begins with this usually)?
Then I will get the hex. representation of the instruction 'goto' and the location of 'Initialize'?

Quote:

Originally Posted by Pommie

You read and write to flash to store/retrieve data. I store messages as 2 x 7 bit ascii characters per location and have filled a 2K bank with text (4000 chars). If you wanted to do a data logger then you can store lots of readings as long as they don't arrive too fast. Bootloaders write code to flash.

Can you give more example? I know that the data can be stored in EEPROM, how about flash memory? Since it is the program memory, how come data is stored there?

Sorry for stating unclearly, but I really want to know.

Thanks

Gayan Soyza · 25th July 2007, 04:07 AM

I think bananasiong asking if the instructions still there after power OFF & ON then why need a special EEPROM location.

He is asking why not keep all the EEPROM Read /Write codings as like a normal program (without writing to EEPROM)

For example: A COUNTER must stop in “9” & after power OFF & ON it must start from “9”.Then we press a button & store the data in the EEPROM.

He is asking why storing in the EEPROM why not save in the main program?
(Because the instructions are still there in the program they didn’t erase after power OFF)

Is this write?

Pommie · 25th July 2007, 04:45 AM

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.

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23rd July 2007, 09:07 AM	(permalink)
Pommie	The programmer can no longer read or write to the EEPROM. It can however clear it with bulk erase. Mike.

23rd July 2007, 09:45 AM	(permalink)
bananasiong	How about the flash memory in the PIC? Is it another memory that stores the data? __________________ Superman returns..

24th July 2007, 01:08 AM	(permalink)
bananasiong	Any clue? The datasheet states only how to read and write into it. I couldn't find any notes from microchip site too. Does the program memory store the program instructions? __________________ Superman returns..

24th July 2007, 04:36 AM	(permalink)
Gayan Soyza	Program memory stores the program instructions. Data memory consists of EEPROM and RAM memories. For Bananasiong this will be helpful. http://www.mikroe.com/en/books/picbook/2_06chapter.htm __________________ Gayan My Website http://gsmicro.blogspot.com/ Last edited by Gayan Soyza; 24th July 2007 at 04:40 AM.

24th July 2007, 09:14 AM	(permalink)
bananasiong	Still couldn't figure it out. Isn't the program stored in the location start from 0x0000? Then for the flash program memory? To store more program instructions start from the 0x1000? I'm refering to PIC16F88. __________________ Superman returns..

24th July 2007, 09:53 AM	(permalink)
Nigel Goodwin	Page 11, figure 2.1 - shows 4K of program memory from 0x0000 to 0x0FFF - that's it, total program memory. If you try and run the program counter past that end address it loops back to 0x0000 again. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

24th July 2007, 03:09 PM	(permalink)
Pommie	You read and write to flash to store/retrieve data. I store messages as 2 x 7 bit ascii characters per location and have filled a 2K bank with text (4000 chars). If you wanted to do a data logger then you can store lots of readings as long as they don't arrive too fast. Bootloaders write code to flash. One nice thing about the USB enabled pics is the bootloader. The bootloader sits in the first 2K of memory and your program gets sent via USB and is written in the other 30k of flash. Mike.

25th July 2007, 04:07 AM	(permalink)
Gayan Soyza	I think bananasiong asking if the instructions still there after power OFF & ON then why need a special EEPROM location. He is asking why not keep all the EEPROM Read /Write codings as like a normal program (without writing to EEPROM) For example: A COUNTER must stop in “9” & after power OFF & ON it must start from “9”.Then we press a button & store the data in the EEPROM. He is asking why storing in the EEPROM why not save in the main program? (Because the instructions are still there in the program they didn’t erase after power OFF) Is this write? __________________ Gayan My Website http://gsmicro.blogspot.com/

25th July 2007, 04:45 AM	(permalink)
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.