Fair point - good catch, Romasik!
I'm deep into speculation here, but if (presuming I recall correctly), the two FMGC units have different software - in order to provide extra redundancy - then the occasional 4s discrepancy in calculating and transmitting the values between the two causes the "initialise" signal* to be set outside the 2s limitation required by the FCMCs.
I think I might be able to elaborate a little - but again, this is speculation - buyer beware! Regardless of the initialisation values, FCMC1 and FCMC2 have a current value which we'll call y1 and y2.
FMGC1 and FMGC2 each have a value and an "initialise" switch, which we'll call x1 and i1 for FMGC1, x2 and i2 for FMGC2. These are the values that are cross-checked against each other, and one of the causes of the ECAM message is if these values are not equal for more than 2s. If there's a discrepancy in calculation or transmission time between the two FMGCs, it seems that it can take up to 4s for one to "catch up" with the other.
The FCMCs will not 'blindly' update their "y" values with the "x" values sent from their respective FMGC unless the "i" value is true. So for argument's sake let's say FMGC1 transmits x1 and i1 to FCMC1 where i1 is "true", but there's a delay of over 2s before FMGC2 does the same.
Because i1 is true, FCMC1 will accept the value and set y1 to the same value as x1. If more than 2s passes before FMGC2 transmits x2 and i2, then y2 will still have the previous value - and because (x1,i1) and (x2,i2) are different (which will also make y1 and y2 different), ECAM will throw the error message.
Obviously I can't say for certain if this is indeed the cause of the issue, but as a working hypothesis it seems valid.
* - for non-techies, "boolean" is essentially 1 or 0, effectively yes/no or true/false.
Last edited by DozyWannabe; 21st Jan 2013 at 20:45.