Int 16 Fn FF80  U - Pc Tools V8+ Cptask - Get And Clear ??? Flag           [T]

   AX = FF80h
   BX = 0006h

Return: AX = old state (0000h clear, 0001h set)

Note:  the tested flag is bit 13 of the flags returned by AX=FF80h/BX=0003h