PIC18F4220 data eeprom address

[Guest]

I am gong mad! Can't find the location of the data EEPROM in a PIC18F4220. I tried the usual

#rom 0x2100 = {1,2,3} but it (CCS ICD) won't verify the data so I assume the address is incorrect?

I just want to init the eeprom data at program time. I can read_eeprom and write_eeprom OK so the device seems fine.

Any help much appreciated.

[drh]

Try 0xF00000
_________________
David

[foodwatch]

I use the 18F4550 and the data eeprom begins at 0xf00000. Not sure about yours

[PCM programmer]

[romertz]

I want to store info not volatile in the pic eeprom avoiding to use external memory...
I found for my device this info...

[Ttelmah]

First thing to understand, is that the PIC effectively has three separate 'memory spaces'. The RAM (and your variables therefore), is completely separate from the other memories. Then there is the 'program' flash memory, and finally the EEPROM. The EEPROM, as used inside a program, is 'seen' with it's own addresses from 0 to 255, (or 1023 on some models). However _when programming_, the chip allows this to be programmed as if it sat on the same address bus as the program memory. Where this is, is always defined in the _programming_ specs, _not_ in the normal device info. For most PIC 18 chips, it is at 0xF00000.

What you have printed is the layout of the standard flash program memory, for your chip. It basically runs from address 0, to 0x7FFF. The 'blocks', have significance, only really when dealing with things like write protection for the boot block etc., which individual fuses control. You don't have to get involved in this at all.

All you do to put data into the EEPROM, when programming the chip, is declare a #ROM block at 0xF00000. Nothing else.

Best Wishes

[romertz]

well. . .i am a little confused. . . . .
The #rom is used when i want to write constant data, right?. . . .but if I want to write variable data that would be necessary even if the pic has been reseted. . . . I could use the write_eeprom instruction, right?.....but I have not found the document where says this address that I have seen a lot. . .the 0xF00000. . . .but, If I use this rom address, and it works....when I would to write the next byte using write_eeprom, what address must I to point?. . . . I mean, I would use for example write_eeprom(0xf00000,data1), to write a 8 bits data at address 0xf00000, if I want to write another 8 bits data consecutive the last. . .
I would write write_eeprom(0xf00008,data2)?....or how must I to point to the address as the length of the data I have wrote before. . .

Thanks for answer, and sorry if this is obvious....

[PCM programmer]

[romertz]

yes right. . . .thanks for your reply . . .i was expecting find in that spec some like start and end....or something that let me know how many memory can i use. . . .i tried with write_eeprom starting in 0 and go until 100. . . .and it seems not have problems. . . .but. . .how could i know the max I can write. . . .
. . . it is working. . . but i am still with the doubt. . . thanks again. . .
. . . lucky is what i wish for you. . .

[PCM programmer]

Look at this table (on page 5) in the 18F4220 Programming specification:

[romertz]

ohhh.....i feel fool seeing that easy.....i guess that looked in the wrong places.....

...thanks very much...bye