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3. CIRCUIT DESCRIPTION
NOTE: In this chapter, the following are assumed.
*The-deck is initially in Stop mode unless
otherwise specified.
*Voltages, waveforms, and operating times,
etc. are given simply for reference in the
. text,
CONTROL
SECTION
3-1. SYSTEM CONTROL
OUTLINED ©
The TASCAM
133B system is extensively con-
trolled by an LS! controller (microprocessor).
Control operations are outlined below.
The operating keys such as REC and PLAY have
their output lines connected to lines DO to 07
of an 8-bit input port of a digital multiplexer.
When one depresses an operating key, an H-level
signal comes into the line of the input port to
which the key is connectéd? On the other hand,
the controller
has a program
which
controls
operating
modes. and provides a 3-bit address
code indicating the associated operating mode
through its output ports (CO, C1, and C2) to
Multiplexer
Operating keys
Logical operation
Inverter
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the input ports (SO, S1, and S2) of the multi-
plexer.
The
mu Itiplexer ANDs
the operating
code with the address code and, if the command
of the operating key is the same as that indenti-
fied by the address, the multiplexer develops L-
level signal through its output port (OUT). This
signal, after inverted to H-level, is applied to port
A3 of the controller. Now the controller knows
that the control command
has been given and
generates signals required for executing the con-
tral command according to the program stored, in
the proper sequence and timing.
The deck has another digital multiplexer. This
worksto resume playback at the end of rewind-
ing to the beginning of tape or to a location
whose-counter reading-has been preset; to main-
tain Stop mode; or to rewind tape which is ata
halt-by CUE STOP. operation, .ln operation, 'this
multiplexer simply controls such operations of
tape .as rewinding; stopping, 'and:playing'on the:
proper timing, and each operation is basically
the same as of the multiplexer described first.
"Detaited description will-be given ater.
Controller
¢2| to through CO-C2
{is executed.
"H" when command
4s-identified
"L™ when command
is not identified.
Fig. 3-1.
System control outlined
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