Circuit Description - Roland CR-5000 Service Notes

CR-5000/8000
9
li?
20
21
22 23 24 25 26
CPU BOARD
a
ic2, pin
12
I
nr
B
CPU BOARD
IC10, Pin 8
CPU BOARD
-1
cycle
-
IC6,
Pin
5
uir
ur
CPU BOARD
.
_,
,_, „_,,
,„_
ic6
-
^
«
^jTirinriTL
CPU BOARD
IC6, Pin
3
CPU BOARD
IC6,
Pin
2
iun
ur
CONDITION
PANEL CONTROLS
BANK
1
LED
"ON"
(ALL THE REMAINDERS "OFF")
(or
PCWER
ON,
RHYTHM STOP)
Fig.
2
CIRCUIT DESCRIPTION
SWITCH
SCANNING
CPU holds one
of
switch matrix rows low through
LATCH IC1 and DECODER IC6.
Exp.
When Sll closes while
pin
4
of
IC6
(B in Fig.
lj is
held low, pin
14
of
BUFFER
IC1
(A
in Fig.
1)
which
is
pulled up via
Rl
,
becomes
low.
This low
is
read
by
CPU
through data
bus.
CPU continues this sequence for the remaining
7
matrix rows
((|), Fig. 2).
Once rhythm starts, time interval between switch scanning varies
to
Tempo Clock
rate.
LED DINAMIC SCANNING
To light LED that
is on,
CPU selects matrix
row and column where the
LED
is
connected
diagonally.
In
the
above example Dll has been
on,
CPU
fires LED driver Ql through LATCH
IC2
in
sympathy with low at
B in Fig. 1 ((a)
and
(5)
in Fig. 2.)
Lengths of lows and intervals between lows
in Fig.
2
ulso vary greatly with controls
setting and rhythm
tempo.
VOICE
TRIGGER SIGNAL
CPU delivers trigger signals (negative
going") to
individual VOICE Generators.
Trigger signal goes negative at the falling edge
of
tempo clock and stays low until
the next falling edge of the
tempo clock. That
is,
width of trigger signal
is
equal
to
period of one clock signal.
The
maxima
trigger signal rate
is
24
clocks
: (
J>
)
.
EXT TRIGGER Derived from LATCH IC1 on CPU board,
"hey are also negative going
and the pulse
width
is
equal to
that of tempo clock.
RESTART
CPU reads
INT
terminal
(
not in
use for interrupt application) every 3ms and
,
when
INT
is
high, resets internal
counter
to
revert to
onset of a measure.
Tf monost.able (1/6IC6. C47 and RS9) output
is
high for
a
period shorter than 3ms or