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SAA7824 Datasheet(PDF) 34 Page - NXP Semiconductors |
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SAA7824 Datasheet(HTML) 34 Page - NXP Semiconductors |
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34 / 89 page  2003 Oct 01 34 Philips Semiconductors Product specification CD audio decoder, digital servo and filterless DAC with integrated pre-amp and laser control SAA7824 handbook, full pagewidth DECIMATION FILTER FAST FILTER DEFECT GENERATION PROGRAMMABLE HOLD-OFF SLOW FILTER defect output sat1 sat2 + − MBG421 Fig.22 Block diagram of the defect detector. 7.16.9 HIGH-LEVEL FEATURES 7.16.9.1 Interrupt mechanism and STATUS pin The STATUS pin is an output which can be configured by decoder register 7 and new shadow register C (bank 3) for one of three different modes of operation. These are: • Output the interrupt signal generated by the servo part (it should be noted that the selection of this mode will override all other modes) • Output the decoder status bit (active LOW) selected by decoder register 2 (only available in 4-wire bus mode) • Output DC offset information (it should be noted that this mode is used in conjunction with the decoder status mode; see Section 7.5). Eight signals from the interrupt status register are selectable from the servo part via the interrupt_mask parameter. The interrupt is reset by sending the read high-level status command. The 8 signals are as follows: • Focus lost: dropout of longer than 3 ms • Subcode ready • Subcode absolute seconds changed • Subcode discontinuity detected: new subcode time before previous subcode time, or more than 10 frames later than previous subcode time • Radial error: during radial on-track, no new subcode frame occurs within the time defined by the ‘playwatchtime’ parameter; during radial jump, less than 4 tracks have been crossed during the time defined by the ‘jumpwatchtime’ parameter • Autosequencer state change • Autosequencer error • Subcode interface blocked: the internal decoder interface is being used. It should be noted that if the STATUS pin is configured to output decoder status information [decoder register 7 = XX10 and new shadow register C (bank 3) = X00X] and either the microcontroller writes a different value to decoder register 2 or the decoder interface is enabled then the STATUS output will change. 7.16.9.2 Decoder interface The decoder interface allows decoder and shadow registers to be programmed and subcode Q-channel data to be read via servo commands. The interface is enabled or disabled by the preset latch command (and the xtra_preset parameter). 7.16.9.3 Automatic error handling Three Watchdogs are present: • Focus: detects focus dropout of longer than 3 ms, sets focus lost interrupt, switches off radial and sledge servos and disables the drive-to-disc motor • Radial play: started when radial servo is in on-track mode and a first subcode frame is found; detects when the maximum time between two subcode frames exceeds the time set by the playwatchtime parameter; it then sets the radial error interrupt, switches radial and sledge servos off and puts the disc motor into jump mode • Radial jump: active when radial servo is in long jump or short jump modes; detects when the off-track counter value decreases by less than 4 tracks between two readings (the time interval is set by the jumpwatchtime parameter); it then sets the radial jump error, switches radial and sledge servos off to cancel jump. The focus Watchdog is always active, the radial Watchdogs are selectable via the radcontrol parameter. |
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Similar Description - SAA7824 |
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