HD49235FS Datasheet, PDF (31/41 Pages) Hitachi Semiconductor – Digital Signal Processor for CD

HD49235FS
2. Play Mode
This mode is automatically subdivided into a starting mode (rough servo control) and normal mode
(fine servo control) according to the rate at which sync signals are detected from the disc. The AINTV
and ATH bits in register C (CLV control) select an interval length and threshold value. Starting mode is
used if the number of sync signals in the selected interval is less than the threshold value. Normal mode
is used if the number exceeds the threshold value. Starting and normal modes operate as follows.
Starting Mode: See table 2 for the outputs at the MON and MSTOP pins. The PWM pin outputs a
rectangular wave with a duty cycle corresponding to the arithmetic mean of the pulse width on the 11-T
low side and 11-T high side in the sync signal detected from the disc. See the PWM output duty cycle
characteristic in figure 18.
Center during play
100
92.1
83.5
79.5
74.8
70.9
66.9
64.6
58.3
54.3
52.0
45.7
41.7
39.4
33.1
29.1
25.2
Center of S-curve of starting servo
Gain: +6 dB
Gain: 0 dB
Gain: –6 dB
PWL PWH
Sync pattern
11T
Fast rotation
0
–4.6 –2.3 ^{–0.300.85} 2.3 4.6
Slow rotation
6.9 9.2
PWL + PWH
2
11T – 1 × 100 [%]
Figure 18 Duty Cycle Characteristic of PWM Output (Speed Error) in CLV Starting Mode
Rev.2, Aug. 1995, page 31 of 41