INT 15,84 - Joy-Stick Support

	AH = 84h
	DX = 0 to read the current switch settings
	   = 1 to read the joystick position (resistive inputs)


	on return (DX=0, read switch setting):
	CF = 0 if successful
	   = 1 if error
	AH = 80h error code if CF set on PC
	   = 86h error code if CF set on XT before 11/8/82
	AL = switch settings in bits 7-4 (if read switch function)

	on return (DX=1, read joystick position):
	AX = A(X)
	BX = A(Y)
	CX = B(X)
	DX = B(Y)