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Circuit Descriptions and List of Abbreviations
EN 79DVD963SA 9.
• The Servo Processor/Decoder
• The Interface/Program Memory
The Loader Interface
The TZA1033HL/K2 (or DVDALAS2plus, item 7105) is an
analogue pre-processor and laser supply circuit. It contains
data amplifiers and several options for radial tracking and focus
control.
It is possible to optimise the dynamic range of this pre-amp/
processor combination for the LF servo and RF data paths. The
gain in both channels is separately programmable. This will
guarantee an optimal playability for all kind of discs.
Also, a dual laser supply is implemented, with fully automatic
laser control including stabilisation and an ON/OFF switch, plus
a separate supply pin for power efficiency.
The Servo Processor/Decoder
In the SD3.0 module, the servo signals were fed to the MACE2
servo processor, while the HF output signal was fed to the
SAA7335 decoder. In the new SD4.0SA_CH module, these ICs
are combined into one chip: the SAA7812 Iguana.
This chip contains the following blocks: channel decoder, block
decoder, servo processor, and microcontroller.
The servo circuit in the SAA7812 (item 7207) takes care of the
servo controls.
In a CD system, there are some twelve control loops active.
About six of them are needed to adjust the servo error signals
that is once per disc rotation. It also adjusts offsets, signal
amplitudes, and loop gains (AGCs), to enlarge system
robustness and to avoid expensive potentiometer adjustments
in production.
The other six loops determine the laser spot position on the
disc in the radial, axial (focus), and tangential directions.
It also has to take care that the spot accesses a required
position as fast as possible. This access system consists of two
parts, namely the actuator and the sled, which are (within a
certain range) mechanically and electrically independent.
Therefore, during an access, the servo has to control as well
the actuator as the sled.
The analogue signals, from the diode pre-processor, are
converted into a digital representation using A/D converters.
For the communication between the host processor (STi55xx)
and the servo processor, the S2B bus is used. This bus
supports full-duplex asynchronous communication.
The SAA7812 is also a combined CD/DVD compatible
decoding device. The device operates with built in hardware for
CD/DVD error correction and de-interleaving operations. It
decodes EFM or EFM+HF signals directly from the laser pre-
amplifier, including analogue front-end, PLL data recovery,
demodulation, and error correction.
Its analogue front-end input (the channel decoder), converts
the HF input signal to the digital domain via an 8-bit ADC,
preceded by an AGC circuit to obtain the optimum performance
from the converter. An external resonator clocks this block.
This subsystem recovers the data from the channel stream. It
corrects asymmetry, performs noise filtering and equalisation,
and finally recovers the bit clock and data from the channel
using a digital PLL.
The demodulator part detects the frame synchronisation
signals and decodes the EFM (14 bit) and EFM+ (16 bit) data
and sub-code words into 8-bit symbols. Via the serial output
interface, the I
2
S data (audio and video) go to the DVD decoder
STi55xx.
The spindle-motor interface provides both motor control signals
from the demodulator and, in addition, contains a tachometer
loop that accepts tachometer pulses from the motor unit. They
drive the motor IC (BA6665FM, item 7300).
The SAA7812 has two independent microcontroller interfaces.
The first is a serial I
2
C-bus and the second is a standard 8-bit
multiplexed parallel interface. Both of these interfaces provide
access to 32 8-bit registers for control and status.
The Interface/Program Memory
The interface between front-end (SAA7812) and back-end
(Sti55xx) is via:
•I
2
S bus (BCLK, DATA, WCLK, FLAG, SYNC and V4).
• S2B bus (RXD_S2B, TXD_S2B, CPR_S2B and
SUR_S2B).
• Miscellaneous I/O ports (RSTNF= front-end reset, EANF=
front-end processor boot select).
Service tip: These lines contain series resistors (47 or 100 Ω)
for easy hardware debugging, and for EMC/noise reduction of
the high-speed I
2
S lines.
The front-end processor SAA7812 (Iguana) has two boot
modes: normal boot from flash memory, or serial mode.
The boot selection is via the EANF pin. The Iguana, samples
the EANF signal level once during boot-up. Once boot-up is
completed, this pin is no longer used for this purpose.
However, in the SD4.0SA_CH circuit, the EANF is also
connected to the flash memory. Therefore, when this pin is
LOW, the lower 1 Mbits of the memory is accessible.
Conversely, when this pin is HIGH, the upper 1 Mbits is
accessible.
Under front-end normal operation, the program memory (less
than 1 Mbits in size) should reside in the lower bank. Therefore,
the EANF pin should be LOW at all times. Since the actual flash
memory used is 2 Mbits, the upper 1 Mbits is unused. This area
is reserved for possible use by the front-end self-diagnostic
software, or flash download application.
9.3.3 Back-end: the Digital Part
The back-end consists of:
• DVD back-end processor
• SACD DSD processor
• Audio output
• Video output
• Clock factory
• Miscellaneous
DVD Back-end Processor
The SD4.0SA_CH is designed for the Sti55xx family. Some of
the DVD related features of these ICs are:
Figure 9-4 Processor overview
The STi5580 has the same architecture as the STi5508 (used
in earlier DVD generations), and is pin-to-pin compatible.
It works on 3.3 V (V
DD
), and comprises the following functions:
• Video decoder, which supports MPEG1 and MPEG2.
• Audio decoder that supports AC-3, MPEG1, MPEG2, DTS,
PCM, S/PDIF, and MP3.
• PAL/NTSC video encoder with simultaneously Y/C, CVBS,
and RGB/YUV outputs.
• The video encoder supports Closed Caption and allows
MacroVision 7.0/6.1.
• Full screen On Screen Display (OSD) generator.
• Three on-chip PLLs to generate all necessary clocks (as
reference the 27 MHz video clock is used).
Processor overview
Function STi5580 STi5588 STi5519
Basic CD/VCD/DVD decoding X X X
Extra 2-channel of I2S output (PCMDATA3) X X
Karaoke X X
X
DTS X
Audio post processing (equalizer, level meter, etc) X
DVD audio X
Progressive scan at analog video output X
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