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參數(shù)資料
| 型號(hào)： | SAA7378GP |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | Single Chip Digital Servo Processor and Compact Disc Decoder |
| 中文描述： | 單片機(jī)數(shù)字伺服處理器和光盤解碼器 |
| 文件頁數(shù)： | 24/45頁 |
| 文件大?。?/td> | 224K |
| 代理商： | SAA7378GP |
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Philips Semiconductors
Preliminary specification: Version 1.0
May 1995
24
Digital Servo Processor and Compact Disc Decoder (CD7)
SAA7378GP
8.4.4
The access procedure is divided into two different modes, depending upon the requested jump size.
Access
The access procedure makes use of a track counting mechanism, a velocity signal based on a fixed number of tracks passed
within a fixed time interval, a velocity setpoint calculated from the number of tracks to go and a user programmable parameter
indicating the maximum sledge performance.
If the number of tracks to go is greater than brake_distance then the sledge jump mode should be activated else the actuator
jump should be performed. The requested jump size together with the required sledge breaking distance at maximum access
speed defines the value brake_distance.
During the actuator jump mode, velocity control with a PI controller is used for the actuator. The sledge is then continuously
controlled using the filtered value of the radial PID output. All filter parameters (for actuator and sledge) are user
programmable.
In sledge jump mode maximum power (user programmable) is applied to the sledge in the correct direction, while the
actuator becomes idle (the contents of the actuator integrator leaks to zero just after the sledge jump mode is initiated).
8.5
The track position (TPI) signal is a flag which is used to indicate whether the radial spot is positioned on the track, with a
margin of
±
1/4 of the track-pitch. In combination with the radial polarity flag (RP) the relative spot position over the tracks
can be determined. These signals are, however afflicted with some uncertainties caused by:
disc defects such as scratches and fingerprints.
the HF information on the disc, which is considered as noise by the detector signals.
In order to determine the spot position with sufficient accuracy, extra conditions are necessary to generate a track loss (TL)
signal as well as an off-track counter value. These extra conditions influence the maximum speed and this implies that,
internally, one of the three following counting states is selected:
Off Track Counting
1.
Protected state: used in normal play situations.
A good protection against false detection caused by disc defects is important in this state.
2.
Slow counting state: used in low velocity track jump situations.
In this state a fast response is important rather than the protection against disc defects (if the phase
relationship between TL and RP of 1/2
π
radians is affected too much, the direction cannot be determined
accurately anymore).
3.
Fast counting state: used in high velocity track jump situations.
Highest obtainable velocity is the most important feature in this state.
8.6
A defect detection circuit is incorporated into the SAA7378. If a defect is detected, the radial and focus error signals may be
zeroed, resulting in better playability. The defect detector can be switched off, applied only to focus control, or applied to both
focus and radial controls under software control (part of foc_parm1).
The defect detector (Figure 17) has programmable setpoints selectable by the parameter, defect_parm
Defect Detection
ACCESS TYPE
JUMP SIZE
1 - brake_distance
1
brake_distance
1
- 32768
ACCESS SPEED
Actuator jump
decreasing velocity
maximum power to sledge
1
Sledge jump
1
: microprocessor presettable
Figure 17 Defect Detector Block Diagram
Sat1
+
-
Fast
filter
Decimation
filter
Defect
generation
Programmable
hold-off
Sat2
Slow
filter
Defect
Out
+
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| SAA7380 | Error correction and host interface IC for CD-ROM ELM |
| SAA7380GP | Error correction and host interface IC for CD-ROM ELM |
| SAA7381 | ATAPI CD-R block decoder |
| SAA7382GP | Error correction and host interface IC for CD-ROM ELM |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SAA7380 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Error correction and host interface IC for CD-ROM ELM |
| SAA7380GP | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Error correction and host interface IC for CD-ROM ELM |
| SAA7381 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:ATAPI CD-R block decoder |
| SAA7382 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Error correction and host interface IC for CD-ROM ELM |
| SAA7382GP | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Error correction and host interface IC for CD-ROM ELM |
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