Philips SAA7345 User Manual
Page 23
1998 Feb 16
23
Philips Semiconductors
Product specification
CMOS digital decoding IC with RAM for
Compact Disc
SAA7345
O
PERATION MODES
The motor servo has the operation modes as shown in Table 9 and is controlled by the motor mode register
(address 0001).
Table 9 Operation modes.
MODE
DESCRIPTION
Start mode 1
Disc is accelerated by applying a positive voltage to the spindle motor. No decisions are involved
and the PLL is reset. No disc speed information is available for the microcontroller.
Start mode 2
The disc is accelerated as in Start mode 1, however the PLL will monitor the disc speed. When the
disc reaches 75% of its nominal speed, the controller will switch to Jump mode. The motor status
signals are valid (register 0010).
Jump mode
Motor servo enabled but FIFO kept reset at 50%. The audio is muted but it is possible to read the
subcode.
Jump mode 1
Similar to Jump mode but motor integrator is kept at zero. Used for long jumps.
Play mode
FIFO released after resetting to 50%. Audio mute released.
Stop mode 1
Disc is braked by applying a negative voltage to the motor. No decisions are involved.
Stop mode 2
The disc is braked as in Stop mode 1, but the PLL will monitor the disc speed. As soon as the disc
reaches 12% of its nominal speed, the MOTSTOP status signal will go HIGH and switch the motor
servo to off mode.
Off mode
Motor not steered.
P
OWER LIMIT
In Start mode 1, Start mode 2, Stop mode 1 and Stop
mode 2, a fixed positive or negative voltage is applied to
the motor. This voltage can be programmed as a
percentage of the maximum possible voltage via the motor
output configuration register (address 0110) to limit
current drain during start and stop. The following power
limits are possible:
•
100% of maximum (no power limit)
•
75% of maximum
•
50% of maximum
•
37% of maximum.
L
OOP CHARACTERISTICS
The gain and cross-over frequencies of the motor control
loop can be programmed via the motor gain and bandwidth
registers (addresses 0100 and 0101). The possible
parameter values are as follows:
Gain: 3.2, 4.0, 6.4, 8.0 12.8, 16, 26.6 or 32.
Cross-over frequency, f
4
:
−
0.5,
−
0.7,
−
1.4 or
−
2.8 Hz.
Cross-over frequency, f
3
:
−
0.85,
−
1.71 or
−
3.42 Hz.
FIFO
OVERFLOW
If FIFO overflow occurs during Play mode (e.g. as a result
of motor shock), the FIFO will be automatically reset
to 50% and the audio interpolator is activated to minimize
the effect of data loss.