MC
‐
BUS
SYSTEM
©
Cyrus
Audio
Ltd
Jun
2014
12
CD
t
Service
Manual
Issue
1
The
MC
‐
BUS
system
MC
‐
BUS
is
a
system
which
provides
communication
between
the
control
systems
of
a
number
of
Cyrus
products.
The
communication
takes
the
form
of
a
serial
data
stream
which
is
sent
from
a
'master'
product
and
received
and
repeated
by
'slave'
products.
The
data
is
thus
passed
from
one
product
to
another
around
a
loop.
The
master
product
should
then
receive
the
message
back
which
confirms
that
loop
connections
have
been
correctly
made.
The
CD
player
is
a
'slave'
product
and
listens
for
'CD'
commands
from
the
master
product
in
the
loop
(usually
an
amplifier
or
surround
decoder).
MC
‐
BUS
internal
signal
routing
MC
‐
BUS
control
is
provided
by
the
system
microcontroller
IC701.
The
signals
are
buffered
into
and
out
of
this
IC
as
shown
in
the
diagram,
The
resistor
bias
at
the
MC
‐
BUS
input
ensures
that
the
line
idles
high
(+5V)
if
no
MC
‐
BUS
connection
is
made
to
another
product.
MC
‐
BUS
system
tests
The
MC
‐
BUS
system
can
be
tested
by
connecting
the
CD
player
into
a
known
working
Cyrus
system.
Note
that
MC
‐
BUS
must
be
connected
as
a
closed
loop
as
shown
in
the
diagram
below.
It
is
also
important
to
connect
the
audio
signal
cables
between
components
to
provide
an
adequate
ground
return
path
for
the
MC
‐
BUS
signals.
Switch
on
the
power
to
the
system
and
set
all
components
to
Standby.
Selecting
the
CD
input
on
the
amplifier
or
switching
on
a
surround
decoder
will
now
activate
the
CD
player.
When
the
amplifier
is
set
to
Standby,
all
other
components
connected
to
the
MC
‐
BUS
loop
will
also
set
to
Standby.
CD
player
Amplifier
MC
‐
Bus
output
MC
‐
Bus
output
MC
‐
Bus
input
MC
‐
Bus
input
IC401F
+5V
IC401E
IC401A
IC401B
IC701
MCBus
out
MCBus
in
49
50