Check out the Mitel application notes I think they have a complete example showing a PIC16C something connected to a MM8870.

Steve

-----Original Message-----
From: Anbar <anbar@WN.COM.BR>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Wednesday, April 21, 1999 8:14 AM
Subject: Tone detector MT8870

I would like to take information how can I use CI MT8870 interfacing with the PIC16F84.

Somebody can help me.

Thank you.