saa7803 NXP Semiconductors, saa7803 Datasheet - Page 55

• Manufacturer Part Number: saa7803
• Description: Saa7803 One Chip Cd Audio Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13695
Objective data sheet
Fig 34. Defect detector diagram
R1
R2
86
87
6.7.9.1 Automatic error handling
6.7.7 Defect detection
6.7.8 Off-track detection
6.7.9 High level features
In order to determine the spot position with sufficient accuracy, extra conditions are
necessary to generate a Track Loss signal (TL) and an off-track counter value. These
extra conditions influence the maximum speed and this implies that, internally, one of the
following three counting states is selected:
A defect detection circuit is incorporated into the SAA7803. 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 has programmable set points selectable by the parameter
defect_parm.
During active radial tracking, off-track detection has been released by continuously
monitoring the off-track counter value. The off-track flag becomes valid whenever the
off-track counter value is not equal to zero. Depending on the type of extended S-curve,
the off-track counter is reset after 0.75 extend or at the original track in the 2.25 track
extend mode.
Three watchdogs are present:
•
•
•
•
•
Protected state; used in normal play situations; a good protection against false
detection caused by disc defects is important in this state
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
direction cannot be determined accurately)
Fast counting state; used in high velocity track jump situations; highest obtainable
velocity is the most important feature in this state.
Focus: detects focus dropout of longer than 3 ms, sets focus lost interrupt, switches
off radial and sledge servos, disables drive to disc motor
Radial play: started when radial servo is in on-track mode and a first subcode frame is
found; detects when maximum time between two subcode frames exceeds the time
set by playwatchtime parameter; then sets radial error interrupt, switches radial and
sledge servos off, puts disc motor in jump mode
DECIMATION
FILTER
FILTER
FAST
Rev. 01 — 19 April 2005
FILTER
SLOW
1
2
GENERATION
radians is affected too much, then the
DEFECT
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
PROGRAMMABLE
One chip CD audio device
HOLD-OFF
SAA7803
001aab777
defect
output
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