I know digi cards hold approx 28 days of data, but do they continually just overwrite when they are full? IE day 29 replaces day 1 etc or is it when they are downloaded they are cleared completely?
Think you will find they hold more than 28 days
They hold a lot more than 28 days of records.
A unit of data is recorded for every mode change, and the card holds a certain number of these. The nature of your work determine how many mode changes are recorded per day and hence how many days of data are on the card.
It is fairly typical to find six months of records on a card.
You can see what the earliest record on yours is by scrolling through the dates on the print menu.
Records are only removed once they are overwritten by newer data, downloading just reads them. There is no way to delete data from the card.
Driver cards are designed to hold a minimum of 28 days of data, I can’t remember the exact figure but that minimum figure is based on more activity changes than you’re ever likely to use in a single shift.
In reality you’ll find many drivers cards hold well over 9 months records before getting over-written, sometimes over a year.
Glen A9:
Records are only removed once they are overwritten by newer data, downloading just reads them. There is no way to delete data from the card.
I thought as much! Another driver had told me that if he downloads his card every day then it clears any infringements there may be on his card. I didn’t think this was the case so thanks for conforming for me.
Thanks for all the replies guys.
You can download daily , company can still see infringements ?
i know, another reason why i didnt understand his logic!
elniniol999:
Another driver had told me that if he downloads his card every day then it clears any infringements there may be on his card.
You’ll soon learn that the first sentence above, will almost certainly be followed by a statement of pure ■■■■■■■■ in the next sentence, as above… The more miles you get under your belt, the better your ■■■■■■■■ filter will get 
F-reds:
You’ll soon learn that the first sentence above, we almost certainly be followed by a statement of pure ■■■■■■■■ in the next sentence, as above… The more miles you get under your belt, the better your ■■■■■■■■ filter will get
possibly the best thing ive read this week!! and im sure its 100% fact too. 
tachograph:
In reality you’ll find many drivers cards hold well over 9 months records before getting over-written, sometimes over a year.
Checked mine today - it goes back to February 2015 for driving times etc, even longer for faults/errors.