Function 84h    Read Joystick Input Settings                 (AT, XT/286, PS/2) 
entry   AH      84h 
	DX      00h     to read the current switch settings  (return in AL) 
		01h     to read the resistive inputs 
return  AX      A(X) value 
	BX      A(Y) value 
	CX      B(X) value 
	DX      B(Y) value 
	AL      switch settings (bits 7-4)