Writing & Reading 2 Bytes to/from Flash

Hello,

I want to store and recall 2 Bytes from Flash on a PIC18F27J13 for pairing up a remote control to a mobile unit.
These are RadioID(RF Address) and RadioCH (Channel#) which are both just 8 bit VARs each.
I think I have the basic idea as below but I cannot figure out how to configure Flash programming.
The (2) memory locations ($1800 and $1900) I picked as it looks like my main code is way below.

Although I think this wastes a whole 64Byte block per each, I do not care at the moment.
I did try setting the above VARs to Words instead of Bytes but that did not help.
Reading through various posts I think I need to define an area of memory for these (2) bytes and un-protect them from being written to. However, I have be unable to find any simple examples and am stumped.

Thanks,


'''''''''''''''''''''''''''''''''''''''''''''''''' ''''''''''''''''''''''''''''''
'' Flash Experiments


Flash:


If Push = 0 Then ' Should Increment ID & CH by 1
Pause 10
If Push = 1 Then ' Noise
Return
EndIf
Do
Pause 10
Loop Until Push = 1 ' Wait for User Release
GLED = 1
EraseCode $1800 ' Whole Block of 4 Words $1800 to $1864?
EraseCode $1900
RadioID = RadioID + 1
RadioCH = RadioCH + 1
WriteCode $1803, RadioID ' Writes to 4th Word in Block
WriteCode $1903, RadioCH
ReadCode $1803, RadioID ' Reads from 4th Word in Block
ReadCode $1903, RadioCH
hserout2["RadioID: ", dec RadioID, 13,10]
hserout2["RadioCH: ", dec RadioCH, 13,10]
GLED = 0
EndIf


GoTo Flash


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Melabs manual says

Flash program writes must be enabled in the configuration for the PICmicro MCU at device programming time for ERASECODE to be able to erase.

Have you done this when programming the pic?

I have looked high and low but cannot see where this is set.
What exactly is this called and where can I find it?

(I have the U2 Programmer with version 4.51.)

its in the hardware configuration registers (fuse settings)

Quote:

---

WPFP = PAGE_0
WPCFG = OFF
WPDIS = OFF
WPEND = PAGE_WPFP

---

shown here with default pbp values (no code protection )
it does help if you post you whole code (in code tags) not just snippets, and include what version of pbp used

Richard,

I tried your suggestion but it did not work.
As my whole code is >73,000 characters it will not post.
I am using PBPX 3.0.7.4
The PIC is a PIC18F27J13.

Is my syntax / technique correct?

Thanks,

what syntax ? at no stage have you posted the relevant config fuse settings you have employed.

why not make a small pgm to test the idea

Richard is asking about config settings where watchdog timer, crystal mode, write protect, etc are all set, and what you are doing there.
The program looks right to me tho I have not used it. Except the output doesn’t absolutely verify what was written, only what read back.

Code:

---


verifya var type ' byte or word
verifyb var type '
verified var bit '

EraseCode $1800 ' Whole Block of 4 Words $1800 to $1864?
EraseCode $1900
RadioID = RadioID + 1
RadioCH = RadioCH + 1
WriteCode $1803, RadioID ' Writes to 4th Word in Block
WriteCode $1903, RadioCH

ReadCode $1803, verifya ' Reads from 4th Word in Block
ReadCode $1903, verifyb

verify = 1
if verifya != RadioID then verified = 0
if verifyb != RadioCh then verified = 0

if verify = 1 then
hserout2["RadioID: ", dec RadioID, 13,10]
hserout2["RadioCH: ", dec RadioCH, 13,10]
else
hserout2[“It’s broken :(",13,10]
endif

---

Each PIC controller has different page size that you can WRITE to.

For example if your chip has 64 words page, then you have to read all 64 words, change what you want, then write back the whole 64 words page.

It is a bit clumsy but that is how it works. You cannot change only the words you really want. And if you write less tat the page size, then data will not be written!

So, my suggestion is to make an array, get the page form Flash, make the changes, then store back to Flash the array.

Ioannis

Or, if reading/writing to a whole page of flash program memory does not appeal to you.
You can always switch to a PIC model that has internally EEPROM or add an external Serial EEPROM.

:)

Ioannis,

This is getting more complicated than I figured.
Might you be available to implement this for a fee?
I can send you money in advance via PayPal.

Thanks,

Jay Zebryk
Zebryk Engineering
Southbridge, Massachusetts

I would also suggest adding an external I2C serial eeprom of small size and using it to store your data. Something as small as an 24LC01 1K device.

Zebryk,

1. how many times will your write new values to flash? Flash has less durabilit than EEPROM.

2. how many words will you store to flash? Think ahead in the future.

3. Are you sure that the address you have chosen will be free?

Ioannis

P.S. No fee necessary, we are here to help each other! :) Look at your P.M. also.