Kurzweil K250 - Page 42

3.4 - FUNCTIONAL DESCRIPTIONS
3.4.1 - CPU (Central Processing Unit)
The "Central Processing Unit" (CPU) board controls the
operation of the entire system.
It controls allllO:reads data from
the keyboard and the Front Panel, directs the dialogue
on the LEOs
and
LCD display, controls the bi-directional personal computer port,
and handles
MIDI In, Out and Thru. The CPU board also tells the other
two boards when
to generate sounds, and it coordinates the signals
on the various connectors on the back panel.
The
CPU board contains the following hardware:
*68000 microprocessor
*PROM bank
*RAM bank
*PROM-or-RAM bank
*Interface to Front Panel
*Music Keyboard scanner with interface to keyboard
*Interface to Personal Computer
*MIDI interface
*24 16-bit programmable timers
Of the 16 megabytes of memory addressable by the 68000, the
first 2 Mbytes are reserved for system memory and
I/O. The
remaining 14 Mbytes are reserved for sound file memory located
external to the
CPU board, on the Channel Group Processor board
(CGP).
The CPU board's internal bus is not accessible to the Channel
Group Processor (CGP).
Instead the CGP talks directly to sound file
memory over its own bus. The
CPU communicates with the CGP over
a special interface bus.
It has access to the sound file memory, but
under control of the
CGP.
The CPU board also contains the hardware for handling the
88-note keyboard, including switch debounce circuitry.
Kurzwell 250 Service Manual, Chapter 3
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