Datatek
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So I can confirm details of the chip in the FOB, the data sheet for those interested can be found here https://www.alldatasheet.com/datasheet-pdf/pdf/144239/FREESCALE/MC68HC705K1.html
The device is one time programable. As suggested by someone, the 4 circular pads visible when the batteries are removed are for programming. One is for the programming clock pulse; Two are for data and address; and one is for power. There are 504 bytes of memory but it appears that only 2 bits of each byte are used. The FOB's would seem to be partly programmed during manufacture with just the vehicle specific information added perhaps by JLR.
Programming info is supposedly available at https://mcu.motps.com but I have not checked it out yet.
I have started to do a circuit diagram but with such small components and my aged eyes it's not easy. It's too cold to do it in my workshop where I have a good bench mounted magnifier. Christmas has not helped either.
I'll update if and when I have more info.
Thanks to Brian who provided the FOB's for me to play with.
The device is one time programable. As suggested by someone, the 4 circular pads visible when the batteries are removed are for programming. One is for the programming clock pulse; Two are for data and address; and one is for power. There are 504 bytes of memory but it appears that only 2 bits of each byte are used. The FOB's would seem to be partly programmed during manufacture with just the vehicle specific information added perhaps by JLR.
Programming info is supposedly available at https://mcu.motps.com but I have not checked it out yet.
I have started to do a circuit diagram but with such small components and my aged eyes it's not easy. It's too cold to do it in my workshop where I have a good bench mounted magnifier. Christmas has not helped either.
I'll update if and when I have more info.
Thanks to Brian who provided the FOB's for me to play with.
