Eventide Ultra-Harmonizer H3000 - Page 5

The
Host
Interface
In
interfacing
with
the
PELs,
the
host
has
two
main
functions.
First,
before
anything
can
happen,
the
host
must
load
executable
code
into
the
program
memory
of
the
PELs.
Once
the
PELs
are
up
and
running,
the
host
must
then
control
various
parameters
of
the
signal
processing
algorithm.
The
host
transfers
data
to
the
PELs
with.two
Sixteen
bit
registers,
the
Host
Address
Register
and
the
Host
Data
Register.
These
registers
form
a
unidirectional
bridge
from
the
6809
to
the
global
bus.
The
6809
can
write
to
the
host
The
Host
Address
Register
is
used
in
two
different
ways,
depending
on
whether
program
code
is
to
be
transferred
or
parameters
are
to
be
changed.
When
code
is
to
be
In
both
cases,
the
PELs
must
execute
code
to
read
the
host
interface.
In
the
case
of
loading
programs
into
PELs,
this
code
is
located
in
the
boot
ROMs
and
is
executed
after
the
host
resets
the
PELs.
For
Parameter
changes,
the
code
must
be
inserted
into
the
program
loops
of
each
of
the
signal
processing
programs.
Mailboxes
For
inter-PEL
communication,
there
are
three
sixteen
bit
registers
called
"Mailboxes".
The
mailboxes
enable
one
processor
to
"deliver"
a
message,
to
be
Picked
up
at
a
later
time
by
another
processor,
or,
by
the
host.
They
are
the
primary
communications
link
between
the
processors.
Typically,
the
messages
exchanged
represent
audio
Signals
traveling
from
PEL
to
PEL,
|
The
mailboxes
are
attached
to
the
global
bus
and
сап
be
accessed
every
processor
cycle.
This
enables
many
messages
to
be
passed
between
processors
during
the
course
of