Sony SEQ-555ES - Page 12

SEQ-555ES
ICsog,509 (MULTIPLEXER)
This is an input selection IC, and determines the pin
to be selected by combinations of signals of pins
@, @ and @.
The truth table is given below.
© | @ | @ | @ onPin
INH A B C
Ee Sg 2) 6. Sse -@
ol) ee ee 1
Be} te. SS Pate. |e
L | L|H | H |] 3
L}|H]|LI] LI 4
L | AH]L] Hi] 5
L | H/| Hj] Li] 6
L H H H 7
DC voltage of the frequency selected at the multi-
plexer is sent to the A/D converter via the logarithmic
amp.
ICsos (MICROCOMPUTER D)
The main functions of this microcomputer are A/D
converter (ICs97) control and LCD display control.
It operates independently of microcomputer B, and
microcomputer B receives A/D converted data from
microcomputer D only during acoustic compensation.
Multiplexer control signals (@, ©~@®) are output
from microcomputer D and the frequency to be
selected is determined.
Next,
a
start
signal
is
sent
from
pin
9
to
start
the
A/D
converter.
When
the
A/D
converter
receives
this
signal,
it
divides
that
frequency
voltage
into
a
6
bit
(64
step)
digital
signal.
When
this
conversion
is
completed,
an
END
signal
is
output
from
the
A/D
converter.
Then
micro-
computer
D
aplies
6
pulses
to
the
CE
pin.
This
pulse
enables
reception
of
the
serial
data
output
from
A/D
converter
pin
@).
During
acoustic
compensation,
microcomputer
B
receives
this
data,
and
stores
the
data
in
the
RAM.
This
data
is
simultaneously
sent
by
microcomputer
C
to
the
LCD
display
circuit
and
lights
up
the
LCD.
For
other
than
acoustic
compensation
A/D
con-
version
as
LCD
display
data
takes
place.
Pin Functions
Pin
@
:
ICs,
(multiplexer)
switching
signal.
Pin
@
:
LCD
display
use
output
signal.
Pin
@,®~@®:
Output
pins
for
frequency
selec-
tion
signal
output.
Pin @ : Strobe signal for LCD display.
Pin
@®
:
Clock
signal
output
pin.
Pins @, @): LCD display data output pin.
Pin @3: Reset signal input pin.
Pin @: A/D converter END signal input pin.
Pin @: Data input from A/D converter.
Pin : Chip enable output to A/D converter.
Pin : Start signal output to A/D converter.
ICso, (MICROCOMPUTER B)
This microcomputer controls the entire system and
interacts with microcomputers A, C and D to control
them.
Pin Functions
Pins @~@) control the 8 ASP IC’s.
The upper 3 bits of each ASP IC correspond to the
chip select pin (CS), and each pin is set as follows.
000 001 010 orl 100
ICios ICxo9 ICiio Gri Irie
CX7976 CX7976 CX7976 CX7976 OX7976
101 110 110
ICyos ICasi IC352
CX7978 CX7977 CX7977
Pin @: Output pin for ASP clock signal.
Pin @: ASP data signal output pin.
Pin @: ASP strobe signal output pin.
Pins @~@ control which IC is to be selected.
ICiog~1i2 form the equalizer volume circuit, and
by controlling these IC’s, each frequency is con-
trolled UP or DOWN. ICio3 performs level UP/DOWN
and operates as a 2dB step volume.
1C351,352 are input selection IC’s.
Pins @)~@) are analog signal switching signals, and
are as follows:
Pin ©): PINK NOISE/LINE H: PINK NOISE
switching
Pin @): MIC/LINE H: MIC
Pin @: +6dB/+12dB H: +6dB
Pin : MUTING H: MUTING ON
Pins () and © are low except during acoustic com-
pensation.
(Pin @ can be switched between H/L.)
Pin @) inputs the interrupt signal output by micro-
computer A before it sends data to microcomputer B.
When interrupt is received, an interrupt permission
signal is output from pin @ to microcomputer A.
Pins @) and @) output REC OUT MUTING circuit
control signals.
When high, REC MUTING turns ON.
MUTING is turned on so that TAPE, signal is not
output to REC OUT, and TAPE, signal is not output
to REC OUT,.
Pin @ outputs an interrupt signal before data is sent
to microcomputer C.