Revox C221

Service
Manual
C221 CD
Player
nd/ox
4.4 Front board
The
front board contains
the following circuits
.
Keypad
.
Display
The
front
board
is connected
to the converter board
by two 6-
conductor
flat cables.
4.4.1
Keypad
The
keypad comprises
25 momentary action
push
buttons.
The
LOAD key
is connected directly
to the interrupt
input of
the
microprocessor
(lNT0).
The
switching
states of
the
other
24
keys
are
periodically
scanned
by
the
microprocessor
via
the output
port
lC7 and input
port
lC8,
both of
which are located on
the
converler
board.
4.4.2 Display
The
microprocessor
controls the
display
serially via
the four lines
SDATA,
SCLOCK,
DIGENABLE and
LDENABLE. The display
consists
of five
7-segment elements with 2
positions
each,
and
7
LEDs.
.
The 7-segment displays
show the title
(track),
index, seconds,
minutes and frames.
.
The LEDs indicate
the
operating states
(ON
LINE, READY, ON
AIR)
and
the activated functions such as fader, auto
pause,
and auto cue.
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