Jacek,

Are you sure the encoder is giving you absolute position as opposed to relative! ?

If it is relative, it will probably be the change of possition since the last sent value. Make sure you sign extend the 12th bit into bits 15,14,13 and 12 before doing a 16 bit addition to the previous position. That is, if bit 11 (12th bit) is set, then add 0xf000 to the 12 bit number. Then you can correctly add to a 16 bit absolute position variable.

<>< Lance.