.MlQ..
- This digitizer input is a 200 mVPP full scale, input. It
has a 47K ohm input impedance and accepts a 1/4 inch phone
jack.
Line
In
- This digitizer input
i~
a 1 VPP full scale input (300
mV
rms). It has a 10K ohm input impedance and accepts a 1/4
inch phone jack.
Front
Panel
Control
Interface
The Front Panel Control Interface circuitry is located
on
the
CPU board. It consists of an 8 bit bi-directional data port, and
eight control lines. The
CPU communicates with the control panel
through the data port. The front Panel
Control Interface consists
of:
*LCD Interface
*Switch/LED Interace
* AID Interface
Keyboard
Interface
The Keyboard Interface is
on
the CPU board. It detects
"events" happening at the keyboard, and reports information about
them
to
the CPU. Since the
CPU
may not be able
to
respond
to
events immediately, data is saved until ready for use.
An
event may
be either
an
"attack" (key depression) or a "release" (key released).
When the machine is first plugged in, the keyboard controller
assumes that all the keys are
"at rest". It then requests the
keyboard sensor modules
to
examine each key 4000 times per
second.
As
long as a key remains "at rest", the sensors activate the
"Kr" signals when the key is examined. The key is said
to
be
"at
rest". When a key is pressed down, though, "Kr"
is
no
longer
activated.
If it is pressed down for long enough, the "Kd" will
be
activated but this does not happen right away, so for a while
neither the
"Kr" nor "Kd" is active.
Kurzwell
250
Service Manual, Chapter 3
3 - 1 3
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