3.4.2 - Channel Group Processor (CGP)
The Channel Group Processor
(CGP)"
board acts
an
intermediary
/-
between the
CPU
and channels. It has,
in
a large memory, definition
for
all the sounds the instrument
can
produce.
On
command from the
CPU,
it will send any sound
in
the memory
to
designated channel (or
multiple sounds to multiple channels).
The soundfile memory
is
a dual-ported, dual-mode array of
memories which have a maximum of 14 Megabytes of
total address
range.
The
two ports are the
CPU
and
the
CGP.
The two modes are
sound
and
data.
The
CGP
performs four functions:
1.
Fetching
(OMA)
sound samples from main memory
2.
Buffering of
up
to
16
sound samples
in
(FIFO)
3.
Servicing of requests for sound samples from
up
to
12
channels (one per sampling clock tick)
4.
Interrupting the main process at the end of each waveform,
under microprogram
control
Each port has its own address strobe (CGASI for the
CGP,
SFASI for the CPU). This indicates to the memory controller
PAL
that a request is pending, and will initiate arbitration of the
soundfile memory.
In
both devices, the request will remain stable
until
an
acknowledge (SFACKI is given to the appropriate device. If
no
request is active, the controller PAL will initiate a
RAM
refresh
cycle.
Kurzwell 250 Service Manual, Chapter 3
3·
1 6
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