rGPGCON &= ~((3<<12)|(3<<4)|(3<<22)|(3<<6))
3<<12
=0000000000000000011000000000000
3<<4
=0000000000000000000000000110000
3<<22
=0000000011000000000000000000000
3<<6
=0000000000000000000000011000000
(3<<12)|(3<<4)|(3<<22)|(3<<6)
=0000000011000000011000011110000
~((3<<12)|(3<<4)|(3<<22)|(3<<6))
=1111111100111111100111100001111
rGPGCON &= ~((3<<12)|(3<<4)|(3<<22)|(3<<6))
就是把rGPGCON的第4,5,6,7,12,13,22,23位(从右往左分别为0-31bit)置0