Sequential prophet 5 - Status Bytes

*;•
6-3 STATUS
BYTES
The
Prophet-5
never
volunteers
DATA
FROM, it only
transmits when
prompted
by
the
sequencer.
Communication
is
initiated
by the
sequencer transmitting
"status"
bytes
which
may
or may
not
signify
that
data
follows. For example,
to
change
programs
the
sequencer
first
sends
a
byte
to the
Prophet saying that the
next byte
is
the
new
program
number.
The
Prophet
will then
wait
for
the new program
byte, and
change
its
program
when
the
second
byte is
received.
There
are
13
unique
status
bytes. A status byte is
simply
a unique
hexadecimal
(H)
number. It
is
distinguished
from other bytes merely
by being
the first
which
the
sequencer
transmits
to the
Prophet
as part of any
data
transfer. The
Prophet
requires
-
1-1/2 milliseconds
(worst case) to respond to
the status
byte
interrupt.
It will
then
be
ready
to
receive
or
transmit data
which is formatted
and
timed
as specified
below.
Generally,
while
data can
be transmitted with
spaces
of between
1 to 'f
ms
between
bytes
without
causing
errors,
you
will
probably want
to operate
faster
for the
most
transparent
operation. Most
of
the
Prophet's
receiving
operations
are
accompanied
by
a
"time-out"
which declares an error if
data is not received
within *
ms.
When
any
error is
detected, the
Prophet simply
ignores the received
data
and resets
to wait
for
another status byte. So
if
data
arrives
too late,
or you
accidentally
send
more data
than needed, the
Prophet
may interpret the
data as a
status
byte.
The Prophet will not accept status
bytes during
its TUNE
routine.
During
TUNE,
DATA FROM transmits
a
BREAK
signal to tell
the
sequencer the
Prophet
isn't
listening.
The BREAK
is simply a continuous
low
on
DATA
FROM.
In other
words, your
receiver
will see a start bit followed
by no stop bit.
The
break
can
therefore
be
detected by counting
at least two
framing errors
with
zero
as
data
received.
(Provided that
the receiver
is being
constantly clocked.)
The BREAK
can
therefore
be
used to inhibit
the sequencer.
6-4
STATUS
0: SEND
KEYBOARD and
BANK/PROGRAM
BYTES
This
status byte is
used
for
the sequencer to record
the
Prophet's keyboard
and "sound"
program
status.
Code 01(H) on DATA
TO
interrupts
the Prophet
to read
its
keyboard.
After
a
-
2-ms
(worst-case) delay to
respond to the
interrupt,
the Prophet
transmits
eight bytes
of keyboard
information over DATA
FROM.
As
mapped below,
61
of the
€>i^
bits represent
key
status (three aren't used).
means
the key is
off ("up"),
1 means
the
key
is on
("down").
As shown, the
least-significant
bit (LSB)
of the
first byte
is the
lowest
C
(CO).
LSB
MSB
Byte
CO
C#0
DO
D//0
EO
FO
F#0 GO
Byte 1
G#0 AO
A//0 BO
CI
C#l Dl
D#l
Byte 2
El Fl
F#l
Gl
G#l Al A#l
Bl
Byte
3
C2 C#2
D2
D#2
E2 F2
F#2
G2
Byte k
G//2
A2 A//2
B2
C3
C//3 D3
D#3
Byte
5
E3
F3
F#3
G3 G//3
A3
A//3
B3
Byte
6
CH
C/M
m
mi*
E^
F^
F//* G^
Byte
7
G#^ M
A//^
B4
C5
X XX
CMIOOOD
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6_3