Roland MSQ-700 Service Notes page 6
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Also See for MSQ-700:
- Owner's manual (32 pages) ,
- Service notes (19 pages) ,
- Owner's manual (32 pages)
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MSQ-700
SEP., 1984
DCB
In
the DCB mode,
connection between DCB
and
IC3
is as shown below.
' W/RDYB
-►
Rxbusy
RxDB
-
Rxdata
RxCB
- -
RxCLK
SIO
<
!>
DCB
CTSB
-
Txbusy
TxDB
-► Txdata
TxCB
- ►-► TxCLK
(NC)
-MIDI IN
A
8253 OUT 0
-
>
MIDI
31 .25kHz
(H) -► midi OUT
J
RECEIVING MODE
When channel B
receives a one byte data,
IC3
turns W/RDYB
(RxBUSY)
LOW.
When the channel
B
receive
buffer
becomes
full,
the
IC3
informs the CPU via INT that
it has received
data.
The CPU
issues
acknowledge by placing
a low on MI
and IORQ lines respectively,
and
the
INT
is
turned back
to high.
Then
the
CPU
reads
the one byte parallel
data with low CE,
IORQ and RD.
Completion
of
data
read
from the receive
buffer enables
IC3
to
return RxBUSY back to
high.
TRANSMITTING MODE
The
IC3
informs
the CPU via
INT
the status
of transmit buffer and TxBUSY from DCB,
and
accepts
one byte parallel data from the
CPU
in much the
timing
in
Receiving mode,
but
on high RD
and only when
TxBUSY is
inactive
(H at DCB connector)
and the buffer
is empty
The
IC3
transmits
the data
in serial
format
at
31.25K baud,
the rate which is
determined
by the OUT 0
of
IC4.
Tj
T2
Tw
T3
Tx
DATA
y
DATA IN
MIDI
In MIDI mode connection to channel B of
IC3
becomes
as
follows:
RECEIVING MODE
In receiving
MIDI
data,
IC3 samples
a one
byte serial
data on
500kHz,
which
16 times
31.25kHz.
Then
it
interrupts
the CPU so that
the CPU can
read
the
data
from
the
ICS
receive buffer.
Recognizing_INT,
the CPU
acknowledges
it with Ml
and
IORQ,
then reads
the data
by turning
the
following pins
of
IC3
low:
35
(CE),36
(IORQ)
and
32
(RD).
See
the timing chart
in DCB RECEIVING MODE.
TRANSMITTING MODE
IC3 requires
IC1 with INT to
send a one byte
data when
its
transmit buffer
is empty.
IC1
writes data into
IC3 with the
timing
shown
in
the
timing chart
in DCB TRANSMITTING MODE.
TEMPO CLOCK
Once
accommodated
in
the master CPU,
tone
data are stored into
memories
in the
format
below;
whether they are
coming
from DCB or
MIDI.
T ime
Key Event
(e.g. ON)
Key Velocity
Time
Key Event
(e.g. OFF)
1 byte
1 byte
1 byte
1 byte
1 byte
For storing
one
complete
ON and OFF
of a
note,
5 bytes
are necessary.
Although key
velocity data is not
included in DCB,
dummy
value
is
added
to have
compatibility with
MIDI
for
simplified data processing.
The
topic
to be
discussed
here
is
by what
means
the
length
of
note
(
or rest
)
is
measured and stored
in memories.
In
the MSQ-
700,
time
is
referenced to tempo clock,
that
is,
the value of a note or rest
is expressed
in the number of clocks;
on
the
120 clocks
per quarter note basis.
These
clocks are
referred to as CLK120
in the MSQ-700.
CLOCK SOURCES
Four clock sources are made available to the
MSQ-700:
INT
(internal),
TAPE
(FSK
),
MIDI
and SYNC
(DIN SYNC);
all
these
clocks
are
defined
as
CLK24.
This measns
that
24 of
these clocks are equal to a
quarter note in
length.
However,
as
mentioned
above,
the
number
of clocks that equals a quarter note
is
120
in the memory section.
Thus,
CLK24
has
to be multiplied by 5.
The
reason
for
the use of
CLK120
is
to
have higher
time
resolution of tone
data;
the higher the clock
frequency,
the
higher
the time
resolution
can be
obtained
for
the same note
length.
CLOCK SOURCE SELECT
The selection
panel
through
the Slave CPU
CPU
to place
IC2 port C.
of source made f
CLOCK
button
is
and IC4,
causing
Interrupt Select
rom the front
detected by
the
Master
code through
6
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