As
long as neither "Kr" or "Kd" is active, following "rest"· the
key
is
said to be
in
the "falling" state.
When
"Kd" finally becomes active, the key is said
to
have
entered the "down state". At the same time,
an
"attack event"
is
r .
reported to the CPU. This report includes a flag identifying it
as
an
attack, the key number and its time of flight. Time of
fl.ight
is
used
to
determine how hard a key was pressed.
A counter exists for each key. Whenever a key
is
in
the "rest
state", its counter
is· reset to zero. While a key
is
in
the "falling
state", its counter is incremented every quarter-millisecond.
As
soon as the key enters the "down" state, the accumulated count
is
reported (in inverted form) as vulocity.
It
shows how many
quarter-milliseconds the key took to fly between
"rest" and "down"
state. A "release"
is
essentially a mirror image of
an
attack. When
"Kd" ceases to be active, the key enters the "rising state" and its
counter starts incrementing every quarter-millisecond.
As
soon
as
"Kr" becomes active again, the count is reported as time of flight,
tagged
as
a "release event"
and
the key re-enters the rest state.
Kurzwell 250 Service Manual, Chapter 3
3-
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