Hi.
I'm having this weird problem with the MT 8880 chip. Whenever it detects a tone and I try to read it, I get a 5 (or occasionally a 7, but I assume the numbers are sort of irrelevant) instead of the correct number. It detects the correct number of tones and such, so my guess is that it's a problem with either the crystal (yes, it's the right frequency according to the spec) or possibly a gain problem (didn't think of this until I saw other people on the board with gain problems).
I've got it in single-ended mode with a signal transformer (Is that what it's called in english? :) to get the correct impedances towards the phoneline and such.
Oh.. And I confess not using a 8052 chip to control it (Using a FPGA instead) but I'm guessing it doesn't make any difference in this case.

Anyone out there have any ideas what it might be?