SAA7806H NXP [NXP Semiconductors], SAA7806H Datasheet - Page 30

• Manufacturer Part Number: SAA7806H
• Description: One chip automotive CD audio device
• Manufacturer: NXP [NXP Semiconductors]

Philips Semiconductors
9397 750 13697
Objective data sheet
6.6.5.4 Run length 2 pushback detector
6.6.5.5 Available signals for monitoring
If this circuit is switched on, all run length 1 and 2 symbols (invalid run lengths) are pushed
back to run length 3. For RL2s, the circuit will determine the transition that was most likely
to be in error, and shift transition on that edge. This feature should always be turned on,
but can be deselected via register RL2PushBack.
The operation of the bit detector can be monitored by the microcontroller and using an
external pin. Several signals are made available for measurement.
PLL frequency signal:
Monitoring via the microcontroller is done by reading the register PLLIntegrator.
Asymmetry signal:
signal. The signal is in 2-complement form and can be read from register SlicerAssym.
Jitter signal:
in register PLLJitter.
The jitter measurement is done in two steps.
First, the distance between the EFM zero transition and the bit clock zero transition is
measured.
Table 6:
Second, the calculated jitter for the zero transition is averaged using a 10-bit low-pass
filter. The top 8 bits of the filter output can be read back from register PLLJitter. To obtain
the jitter in % of the channel bit clock, the following formula applies:
This jitter measurement is also available via the telemetry signal on pin MEAS. On this
signal, the full 10-bit output of the filter is available - see
measurement signal on MEAS
It is also possible to read out an average jitter value via register PLLAverageJitter. This
value is an average over a period of 8000 bit clocks on the normal jitter value. The formula
to transform this into % is the same:
average jitter
Distance ( f
<
2
4
>
jitter
16
16
2
6
16
16
to
to
4
6
=
16
16
Jitter input calculation
------------------------------------------ -
jitter 7:0
bit
A jitter measurement is done internally. The zero-crossing jitter is available
)
=
1024
average jitter 7:0
------------------------------------------------------------------ -
The second signal that can be monitored is the 8-bit asymmetry
–
Rev. 01 — 20 June 2005
2.83
The first signal that can be monitored is the PLL frequency signal.
100
1024
Average distance (bit clocks) Jitter filter input (5-bit
1
3
5
7
pin”.
16
16
16
16
%
–
2.83
100
One chip automotive CD audio device
%
Section 6.6.5.6 “Format of the
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
decimal integer)
1
9
25
49
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