INT 15 - BIOS - JOYSTICK SUPPORT (XT after 11/8/82,AT,XT286,PS)
AH = 84h
DX = subfunction
0000h read joystick switches
Return: AL bits 7-4 = switch settings
0001h read positions of joysticks
Return: AX = X position of joystick A
BX = Y position of joystick A
CX = X position of joystick B
DX = Y position of joystick B
Return: CF set on error
AH = status
80h invalid command (PC,PCjr)
86h function not supported (other)
CF clear if successful
Notes:  if no game port is installed, subfunction 0000h returns AL=00h (all
switches open) and subfunction 0001h returns AX=BX=CX=DX=0000h
a 250kOhm joystick typically returns 0000h-01A0h


1584 - BIOS - JOYSTICK SUPPORT (XT after 11/8/82,AT,XT286,PS)