Specifications

Chapter 2 Firmware Commands 61
The controller stores only one set of touchdown and liftoff points.
If the screen is touched more than once before the controller
receives a ^Q, the controller reports the most recent touchdown
point only. If a touchdown is reported, it will report the last liftoff
point regardless of how many times liftoff has happened before the
second ^Q is received.
Note that the controller does not send any data in response to the ^Q
request if a user does not touch the screen. The controller holds the
^Q and informs the host system the next time a user touches the
screen. Therefore, the controller will send the X, Y coordinate data to
the host at any time after a ^Q if there was no touch at the time the
host sent the ^Q.
Response: <SOH>0<CR> Positive response.