Korg MEX-8000 - Korg MEX-8000 Circuit Description; Outline and Main Features; Hardware Layout Overview; Error LED Battery Indicator

I
Outllne
The MEX€0@
has
been marketed
as a memory expander,
which is
also capable
of application with
other units capable
of
data
dump for MlDl
data
processing.
I Maln Featuree
1. lnput/output of
MlDl
data
2.
il
Program
setting
memory
in
each of
4 banks
(44
x
4)
3. Selection of connected device
via Device
Switch
DEVICE
Swltch
4.
Changing
of
MlDl
Channel
via
MlDl
CH switch
MlDl CH.
Swltches
5. Protection of data
in various
banks
via PROTECT
switch
PROTECT Swltches
6.
ERROR
LED indication
of
weak batteries
(ERROR
LED
blinks)
EXRON
-H-flå:lT,[,0J,:T'',n
I
Hadware
Layout
(Refer
to
Block
diagram and Circuit
diagram)
The
basic system is made up of a CPU
using
a C-MOS
63803X
(lCS),
64
K EPROM 27il
(lCG)
for
system
program,
and
a
64K CMOS
RAM
62il
(
x 2)
for
program
setting
data.
This
RAM is backed up by a
lithium
battery.
HC139 is
used as a decoder. On
one side
(1/2
HC139)
it is
connected
to the
matrix
switch
for
switch selection,
while on
the other side
(1/2
HC139)
it
decodes address
(A13-415)
se-
lecting
RAM
or
ROM chip.
All
s-witch inputs are
processed
according to system
pro-
gram,
being fed
into
cPU
PoRT
5
(P.54
-
P.sn as
4
bit
SW Data.
All
LEDs light atter
signal
passes
through
LED DRIVER
Mil527
(lC4),
controlled by 6
bit data output through
CPU
PORT6(P.60
-
P.65).
MlDl
DATA is output
via
(MlDl
lN) PORT
24
(fX),
being
fed
in
via
CPU
PORT 23
(RX),
passing
through
Auto-coupler
PC-900
(PC-1).
CPU
PORT
52
is
used
for battery
level
check. Turns
to
"L"
when battery
level
goes
below 6.2V.
Reset
circuits comprise
M83761
(1C10).
sw1
sw2
sw3
sw4
Ilevlce
0 0
0 0
DW€mo/EX€mo
0
0 0
1
DW€000
0
0 1 0 DVP.1
0 0
1
1
POLY-800tr
0
1 0 0 EX-800
0
1
0
1
POLY€OO
+
MDK
0110
1111
Not used
l
However,
if
the connected device
is capable
of
sound
data\
I
dump by itself then LOAD, SAVE
operations
may be
per-
I
I
formed with these switches
set to 0110.
At this time,
Bank
I
\D
may
not
be used.
/
sw1
sw2
sw3
sw4
MIDI
CHANNEL
0 0
0 0 ch1
0 0 0
1
ch2
0 0
1
0 ch3
0 0 1 1 ch4
0
1 0 0 ch5
0
1
0
1
ch6
0
1
1 0 ch7
0
1 1 1 ch8
1
0
0
0 ch9
1
0
0
1 ch 10
1
0
1
0
ch
11
1 0
1 1
ch 12
1
1
0
0 ch
13
1
1
0
1
ch
14
1 1
1
0
ch 15
1 1 1
1 ch
16
sw1
sw2 sw3
sw4
PROTECT
ON
1
1 1
1
PROTECT
OFF
0 0 0
0
5