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Interpolation Circuit
If, when the error correction circuit cannot correct an error, the erroneous audio data is output without any correction, the
result would be excessive noise. In order to reduce this noise, the erroneous data is replaced with a linear approximation
based on the correct data on either side of the incorrect data. When there are two or more C2 flags, the previous data level
is held. However, when new data is output after two or more continuous flags, then a linear approximation is made based
on the correct data and the held value that is two points earlier and the middle point is replaced with this linear
approximation.
* When there is an error in one place
General I/O Ports Pin 33: CONT2, Pin 34: CONT3, Pin 35: CONT4/SFSY, Pin 36: CONT5/PW
The four signal lines, CONT2 to CONT5, have I/O ports. These lines are all input terminals at the time of reset. Unused
ports must either be connected to ground or set as output ports. Moreover, pins 35 and 36 are pins that are shared
(exclusively) as, respectively, the subcode frame sync signal output pin (SFSY) and the subcode output pin (PW). The
selection of the function of these pins is done by commands from the microcontroller.
Note that pin 34 functions as either the subcode readout clock input pin (SBCK) or as CONT3. When this pin is used as
SBCK, the CONT3 input pin mode (output disabled) must be selected.
Code
$DD
$DB
$DC
Code
$F6
$F7
The port data is read out sequentially from CONT2, CONT3, CONT4, and CONT5 with the falling edge of the CQCK
from the SQOUT pin when there is a port read command. The command uses a single-byte command format.
* When a command is applied to this DSP during a track check, track jump, or internal MTR brake operation, then the
DSP will terminate those operations. If you do not wish to terminate these operations, do not apply unnecessary
commands (including general port operation commands) during track check, track jump, or internal MTR brake
operations.
These ports can each be set individual as control output ports by the port I/O set command. The ports are selected by the
lower four bits of a single byte. Starting with the least significant bit, these four bits of this single byte data correspond to
CONT2, CONT3, CONT4, and CONT5. The command uses a two-byte command format (RWC1 set).
* Although the ASRES pin is allocated as the lowest-order bit of the general-purpose I/O port, it may not be used as a
general-purpose I/O port. Applications must set the lowest-order bit in the command code to 0 when setting up the
I/O port I/O direction with a PORT I/O SET command ($DBXX). Note that the system goes to this state after a reset.
LC78626KE
Correct data
Flagged data
Interpolated data
Held at the previous value
COMMAND
PORT READ
PORT I/O SET
PORT OUTPUT
COMMAND
SFSY, PW output enabled
SFSY, PW output disabled
* When there are continuous errors (three errors in this example).
RES = low
PORT I SET
RES = low
A11300
A11301
No. 5995-23/34
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