switch (P1)
{
case 0xfe:while(P1!=0xff); P20=~P20; break;
case 0xfd:while(P1!=0xff);P21=~P21; break;
case 0xfb:while(P1!=0xff); P22=~P22; break;
case 0xf7:while(P1!=0xff); P23=~P23; break;
case 0xef:while(P1!=0xff); P24=~P24; break;
case 0xdf:while(P1!=0xff); P25=~P25; break;
case 0xbf:while(P1!=0xff); P26=~P26; break;
case 0x7f:while(P1!=0xff) P27=~P27;; break;
default: break;
}