The function wait-serial-port-state
waits for some state in the serial port associated with serial-port to change.
The argument keys should be a list of one or more of the keywords :cts
, :dsr
, :err
, :ring
, :rlsd
and :break
.
result is a list giving the keys for which the state has changed.
If timeout is non-nil then the function will return nil
after that many seconds even if the state has not changed.
LispWorks User Guide and Reference Manual - 20 Sep 2017