I had previously asked about a/d lockup when very near Vdd:
"...except when the input voltage gets near +5, the 12F675 "locks" up,"

Please ignore the question, I discovered that if the a/d value was 255, the
program would go off the end of my lookup table - because the table only
has 254 entrys due to the addwf PCL,f at the start, therefore it exceeeds
the page when at 255. As my output is interrupt driven, the output looked
normal but wouldn't respond.
------------------------------------------
                org 0x0200
MSB_Period
                   addwf  PCL,f
                   retlw  0xXX
                   (252 other retlw 0xXX) retlw  0xXX
                   (0x300 page)
--------------------------------------
I didn't count the fence posts correctly :)
John Snider

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.