     $66/102:   FAC Sign

    Kernal-Reference:

     BIT $66     : $BCA2 $BDE1
     EOR $66     : $AE7C $BAA5 $BC69 $BD88
     LDA $66     : $A778 $AE33 $B1BB $B7F7 $B853 $B947 $BAD4 $BBEC $BC2F $BC92
                   $BCBC $BCD7 $BFB8 $E28B $E293 $E30E
     LDX $66     : $B05F
     LSR $66     : $BC58
     STA $66     : $AD49 $B056 $B857 $B8FB $B94B $BAD1 $BBB9 $BBFE $BC53 $BDEA
                   $BFBC $E0E5 $E2CE
     STY $66     : $A9EB $B885 $BCD9