INT 15 - SYSTEM - POINTING DEVICE BIOS INTERFACE (PS) - EXTENDED COMMANDS
        AX = C206h
        BH = subfunction
            00h return device status
                Return: BL = pointing device status (see below)
                        CL = resolution (see AX=C203h)
                        DL = sample rate, reports per second
            01h set scaling at 1:1
            02h set scaling at 2:1
Return: CF set on error
            AH = status (see AX=C200h)

Bitfields for pointing device status:
 bit 0  right button pressed
 bit 1  reserved
 bit 2  left button pressed
 bit 3  reserved
 bit 4  0 if 1:1 scaling, 1 if 2:1 scaling
 bit 5  device enabled
 bit 6  0 if stream mode, 1 if remote mode
 bit 7  reserved

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