write to EEPROM and interrupt

[micro]

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

[Darrel Taylor]

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>

[swr999]

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?

[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.

[rsocor01]

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.

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

[swr999]

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.
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.

[swr999]

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

[swr999]

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.