write to EEPROM and interrupt

i use external interrupt in my programm, and i want to use WRITE command
but i must turn interrupt off or mask it before use WRITE command.
so, how can i do that?? should i put WRITE command at the beginning of the software? i mean before Main loop, or is there any simple methode to do it ??

pic16f84


WRITE_PRO:
---
----
WRITE 3,4
---
--
goto WRITE_PRO

OPTION_REG =%11000000
INTCON =%10010000
ON INTERRUPT GOTO INT

MAIN:
---
----
GOTO MAIN

Did i do the right or the wrong ??? because i want to put WRITE_PRO at any posion not at the beginning as i did

The position in the program will not have any bearing on how WRITE operates. Put it wherever you want it.

If an interrupt occurs in the middle of a WRITE sequence, it can cause the WRITE to fail. But, the interrupt has to happen at just the right time to cause a problem. So turning OFF interrupts everytime isn't always necessary.

I like to try writing to EEPROM with interrupts turned on, to reduce the possibily of losing other interrupts(10ms is a long time).

Do the WRITE, then READ it back to see if the WRITE was successful, if not, try again. If interrupts are happening so fast that it fails 3 times in a row. Then turn off the interrupts (INTCON.7 = 0) and write it one last time.

Unless your interrupts are happening at a very high speed, the write will succeed the first time, 99% of the time or better.
<br>

I'm going to try this. Thanks!

Also, does the same apply to EEPROM reads? I assume a READ instruction can get messed up if the interrupt occurs at just the right time during the READ?

swr999, I have used the "DEFINE WRITE_INT 1" directive with my 18F parts and have had no problems. The READ instructions are not to my knowlege prone to disruption with interrupts enabled.

Quote:

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Originally Posted by Dave

swr999, I have used the "DEFINE WRITE_INT 1" directive with my 18F parts and have had no problems. The READ instructions are not to my knowlege prone to disruption with interrupts enabled.

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Hi. Is this a PBP3 DEFINE? I don't see this in my PBP 2.60 manual. What does it do?

Quote:

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Originally Posted by Dave

swr999, I have used the "DEFINE WRITE_INT 1" directive with my 18F parts and have had no problems. The READ instructions are not to my knowlege prone to disruption with interrupts enabled.

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Thanks Dave. My "issue" is that I have a 10-mS interrupt running to keep track of elapsed time. I have several EEPROM writes and since EEPROM writes take a while I don't want to lose time by stopping the interrupt for every write.

I did a test program where I repeatedly wrote to EEPROM with a 'random' WORD. For each write I then read back the value that got stored in EEPROM. It turns out that the error rate due to interference from the interrupt was quite low, about 0.04% (~400 errors in a million writes). So what I ended up doing was to do each write with a call to a subroutine:

EEwriteWord:
WRITE addr,xW.byte0:WRITE addr+1,xW.byte1
READ addr,xR.byte0: READ addr+1,xR.byte1
IF xR != xW then
INTCON.7=0
WRITE addr,xW.byte0:WRITE addr+1,xW.byte1
INTCON.7=1
ENDIF
RETURN

This seems to be working well. While the EEPROM write takes several mS the READ is pretty fast, so this doesn't add too much overhead.

Quote:

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Originally Posted by rsocor01

Hi. Is this a PBP3 DEFINE? I don't see this in my PBP 2.60 manual. What does it do?

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DEFINE WRITE_INT 1 is used to avoid write errors during a WRITE to EEPROM which might otherwise possibly be caused by an interrupt occurring during the write. The functionality is that it disables interrupts just prior to executing a WRITE instruction, and re-enabls interrupts after the WRITE completes. Appears to be strictly a PBP3 feature.

With regard to the "DEFINE WRITE_INT 1" directive, it appears to be available at least from PBP 2.50 onwards. I misspoke above^^^. Apologies.