SJ-MD100
– 9 –
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Operating Procedures
Play
P1.
To read the signals recorded on the disc, the laser beam emitted by the laser diode (LD) strikes the disc and is reflected back and
detected by the photodetector (PD).
T
For a pre-mastered disc, similar to a CD, the signals are recorded as pits on the surface of the disc, and the signals are
detected by the amount of light reflected when the laser beams strikes the pits.
T
For a recordable disc, the signals are recorded by magnetizing the magnetic film on the surface of the disc and there is no
variation in the amount of light that is reflected, so the signals are detected using the shifting of the polarization of the
reflected light due to the Kerr effect*
1
.
P2.
The detected signals are input to pins 38 and 39 of the RF IC (IC1), where they are amplified and then output from pin 32.
T
By observing the input signals (between pins 38 and 39) and the output signals (pin 32) on an oscilloscope, it is possible to
check the eye pattern.
P3.
Error correction of the amplified signals is performed by the MD LSI (IC3: MN66616) using EFM demodulation and ACIRC*
2
and
the signals are stored in the DRAM (IC72: MNV4400). At this time, the cycle of the signals is adjusted by the LSI's clock in order
to eliminate any jitter that might result from irregular revolution of the disc.
P4.
The signals are sequentially taken from the DRAM (IC72) and sent back to the MD LSI (IC3), where they are ATRAC*
3
-decoded
and then output from pin 64.
All of the above steps 1 through 4 are processed on the MD servo PCB, and all of the signals are digital.
P5.
The digital signals output from the MD LSI are input to pin 13 of the A/D-D/A converter (IC601: AK4520) via the interface IC
(IC401: TC74HCT7007; input: pin 3; output: pin 4), where they are converted to analog signals and then output from pins 26 (left
channel) and 27 (right channel).
P6.
The analog-converted signals are output to LINE OUT via the buffer amp (IC711: BA4560; input: pins 5 (left channel) and 3 (right
channel); output: pins 7 (left channel) and 1 (right channel)). At the same time, they are also output to the headphone amp
(IC801: M5218; input: pins 5 (left channel) and 3 (right channel); output: pins 7 (left channel) and 1 (right channel)).
T
The MD servo PCB operates at Vcc = 3.3 V, and the main PCB operates at Vcc = 5 V. For that reason, the exchange of
signals between the two PCBs is performed via an interface IC (during playback: IC401 (TC74HCT7007); during recording:
IC402 (TC74HCT4050)).
T
The exchange of signals between the DRAM and the MD LSI is performed using four data lines (pins 1, 2, 24, and 25 of the
DRAM and pins 43, 44, 45, and 46 of the MD LSI).
Record
R1.
The analog signals input from LINE IN pass through the REC LEVEL VR and are input to pins 5 (left channel) and 3 (right
channel) of the A/D-D/Aconverter (IC601) via the buffer amp (IC751: BA4560; input: pins 5 (left channel) and 3 (right channel);
output: pins 7 (left channel) and 1 (right channel)).
R2.
The analog signals input to the A/D-D/A converter (IC601) are converted to digital signals with a sampling frequency of fs = 44.1
kHz and then output from pin 14 to pin 65 of the MD LSI (IC3) via the interface IC (IC402: TC74HCT4050 ; input: pin 3; output: pin
4).
R3.
The signals input from OPTICAL IN are input to pins 70 and 71 of the MD LSI (IC3) via the interface IC (IC401; input: pin 9; output:
pin 8).
R4.
The signals input to pins 70 and 71 of the MD LSI (IC3) are converted to a sampling frequency of fs = 44.1 kHz by an fs converter
inside the LSI. If the signals are already fs = 44.1 kHz, they bypass the fs converter.
R5.
The signals converted to fs = 44.1 kHz or the signals input to pin 65 are ATRAC-encoded and stored in the DRAM (IC72).
R6.
The signals are sequentially taken from the DRAM (IC72) and sent theback to the MD LSI (IC3), where they are ACIRC-processed
and EFM-modulated and then output from pin 73 to the magnetic head.
R7.
The magnetic disc records the signals onto the disc by magnetizing the magnetic film on the surface of the disc. During recording
the laser diode emits its laser beam in order to raise the temperature to the Curie temperature*
4
that is required to magnetize the
magnetic film. For this reason, the optical power of the laser diode is higher during recording than during playback.
T
Although the disc revolves at a speed fast enough to write the signals without compression, the recording signals are
compressed in order to reduce the data volume. As a result, the signals are written intermittently rather than continuously
(the recording signals are intermittently sent to the magnetic head).
Control
C1.
Performs the necessary controls for each operation during playback and recording and for writing of the UTOC*
5
at the end of
recording.
T
The information written in the UTOC includes the recorded track numbers and their addresses, text data, etc.
C2.
Performs the necessary displays of the text data recorded on the disc and for each operation.
The system is designed for integrated operation, so that the system control IC (IC10) on the MD servo PCB and the system
control IC (IC901) for the component system mutually exchange data (communicating).
Clock
T
The controls of the playback signal, recording signals, and of the 4-channel driver IC (IC1: AN8772) all function using the clock
on the MD LSI as the master clock.
T
The A/D-D/A converter (IC601) functions by using the clock signal of the MD LSI as the master clock and frequency-sampling
that signal 384 times via the clock generator (IC501: TC9246).
