SAA7374GP PHILIPS [NXP Semiconductors], SAA7374GP Datasheet - Page 23

• Manufacturer Part Number: SAA7374GP
• Description: Low voltage digital servo processor and Compact Disc decoder CD7LV
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
7.13.1.4
In the CDV motor mode, the FIFO position will be put in
pulse-width modulated form on the MOTO1 pin [carrier
frequency (300
The PLL frequency signal will be put in pulse-density
modulated form (carrier frequency 4.23
MOTO2 pin. The integrated motor servo is disabled in this
mode.
The PWM signal on MOTO1 corresponds to a total
memory space of 20 frames, therefore the nominal FIFO
position (half full) will result in a PWM output of 60%.
In the lock to-disc (CAV) mode the CDV motor mode is the
only mode that can be used to control the motor.
7.13.2
The motor servo has the following operation modes
controlled by register 1 (see Table 9).
In the SAA7374 decoder there is an anti-wind-up mode for
the motor servo, selected via register 1. When the
anti-wind-up mode is activated the motor servo integrator
will hold if the motor output saturates.
7.13.2.1
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.
Table 9 Operating modes
1998 Feb 26
Start mode 1
Start mode 2
Jump mode
Jump mode 1
Play mode
Stop mode 1
Stop mode 2
Off mode
Low voltage digital servo processor and
Compact Disc decoder (CD7LV)
MODE
S
PINDLE MOTOR OPERATING MODES
CDV/CAV output mode
Power limit
d) Hz], where ‘d’ is the disc speed factor.
The 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.
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 selectable via register 2 are valid.
Motor servo enabled but FIFO kept reset at 50%, integrator is held. The audio is muted but it is
possible to read the subcode. It should be noted that in the CD-ROM modes the data, on EBU and
the I
Similar to jump mode but motor integrator is kept at zero. Used for long jumps where there is a large
change in disc speed.
FIFO released after resetting to 50%. Audio mute released.
Disc is braked by applying a negative voltage to the motor. No decisions are involved.
The disc is braked as in stop mode 1 but the PLL will monitor the disc speed. As soon as the disc
reaches 12% (or 6%, depending on the programmed brake percentage, via register E) of its
nominal speed, the MOTSTOP status signal will go HIGH and switch the motor servo to Off mode.
Motor not steered.
2
S-bus is not muted.
n MHz) on the
23
DESCRIPTION
This voltage can be programmed as a percentage of the
maximum possible voltage, via register 6, to limit current
drain during start and stop. The following power limits are
possible;
7.13.3
The gain and crossover frequencies of the motor control
loop can be programmed via registers 4 and 5. The
following parameter values are possible;
It should be noted that the crossover frequencies f
are scaled with the overspeed factor ‘n’ whereas the gains
are not.
7.13.4
If FIFO overflow occurs during Play mode (e.g. as a result
of motor rotational shock), the FIFO will be automatically
reset to 50% and the audio interpolator tries to conceal as
much as possible to minimise the effect of data loss.
100% (no power limit), 75%, 50%, or 37% of maximum.
Gains: 3.2, 4.0, 6.4, 8.0, 12.8, 16, 25.6 and 32
Crossover frequency f
1.4
Crossover frequency f
3.42
n Hz, 2.8
L
FIFO
n Hz
OOP CHARACTERISTICS
OVERFLOW
n Hz
4
3
: 0.5
: 0.85
n Hz, 0.7
n Hz, 1.71
Product specification
SAA7374
n Hz,
n Hz,
3
and f
4