Quote Originally Posted by The Master View Post
Hi, my 10M resistors arrived today. Just before i blow myself up (or even worse another PIC :P) i wanna be sure what im doing. Ive looked in the datasheet for my PIC and the only mention of "clamp" is input/output clamp current which is 20mA. Does that mean it has those clamping diodes or is that something else?
What PIC? What pin? The datasheets have diagrams of all the inputs showing the clamping diodes. For example, the 12F683 datasheet section 4.2.5 PIN DESCRIPTIONS AND DIAGRAMS has block diagrams of each pin. All but GP3 have clamping diodes to Vdd & Vss. GP3 only has one to Vss. Every datasheet I've ever seen has a similar section. You can also look at Microchip AN236 to see how they detect ZC in an X-10 application.

If you are concerned about the high voltage then your best bet is to use a wall transformer type of DC power supply. It will give you an isolated DC output of whatever voltage you wish.