I'm having problems reading or writing the EEPROM data memory on a
PIC18F458. I've faithfully copied the simplest piece of code from the
PIC18FXX8 data sheet 5-1 but it doesn't return the correct value. The
value in EECON1 stays at 0xC0 unless you clear EEFS which then allows
EEPGD to be cleared. This is not shown in the example. Whatever address
I select in EEADR (0x00-0xFF) it always returns 0xFF in EEDATA. I know
what is stored at each of these addresses as I have set them using the
following.

                ORG 0xF00000    ;from MPASM help
FLASHVARIABLE   DE 0x12 ;etc Flash memory set using this & viewed ok in
MPLAB window.

There seems to be some confusion in the data sheet PIC18FXX8.PDF as the
diagram 5-1 refers to bit 6 as EEFS in EECON1 whereas diagram 6-1 refers
to bit 6 as CFGS.

The Errata file indicating problems with timing a RD immediately after a
write to EEADR doesn't apply here as the example code doesn't do this.

The device is being accessed using ICD2 and this works fine except for
this issue. You can change the flash data in the MPLAB window so there's
nothing wrong with the chip. My guess is that there is another line
missing from the example but I can't put my finger on it.
Any ideas?

I have also used the sample code for writing to the Data EEPROM and this
doesn't work either. If the EEPROM write interrupt is enabled, I can
trap the interrupt & find the relevant EEPROM write flag bit is indeed
set but the data just doesn't get written.



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