LC78626 Sanyo Semicon Device, LC78626 Datasheet - Page 24

• Manufacturer Part Number: LC78626
• Description: DSP for Compact Disk Players
• Manufacturer: Sanyo Semicon Device

18 The Interpolation Circuit
19 The General I/O Ports Pin 33: CONT2, Pin 34: CONT3, Pin 35: CONT4/SFSY, Pin 36: CONT5/PW
* When a command is applied to this DSP during a track check, track jump, or internal MTR brake operation, then the
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.
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.
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.
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).
Code
Code
$DD
$DB
$DC
$F6
$F7
(1) When there is an error in one place
SFSY, PW output disabled
SFSY, PW output enabled
PORT OUTPUT
PORT I/O SET
PORT READ
COMMAND
COMMAND
Correct data
Flagged data
Interpolated data
Held at the previous value.
LC78626E
(2) When there are continuous errors (three errors in this example).
PORT I SET
RES = low
RES = low
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