TDA7546 Datasheet, PDF (31/68 Pages) STMicroelectronics – Multichip module for TMC tuner applications

TDA7546
Functional description
5.2.6
synchronization control. A software reset “ar_res” rds_int[5] can be used to force
resynchronization.
An endless 2 bit block counter (A, B, C or C’, D, A, B...) increments one step if a new RDS
block was received. During synchronization the block counter is set to the first identified
valid RDS block. Then every next RDS block must be of that type which is indicated by the
block counter “blk” rds_qu[3:2]. If this is not true, then the syndrome becomes not zero
(indicated by “synz” bit rds_qu[0]) and the “data_ok” bit rds_corrp[1] is not set. In case of
USA BRDS, four consecutive E blocks can be received which are indicated by the “e” bit
rds_qu[1].
The quality bit counter rds_qu[7:4] counts the bad quality marked RDS bits within a RDS
block.
The group and block synchronization module extracts also TA, TAEON information and
detects blocks types A, B, D (refer to Table 37) which can be used as interrupt sources.
The TA interrupt is performed in two cases: If within block B the group 0A or 0B is indicated
and the TA bit is set or if within block B group 15B is indicated and the TA bit is set. The
TAEON interrupt is performed, if within block B group 14B is indicated and the TA bit is set.
The interrupts can be recognized on the interrupt flag “int” rds_int[0] (refer to Table 37). The
external open drain pin INTN (15) is the inverted version of the “int” flag.
Flywheel mechanism
Figure 7. Example for flywheel mechanism
100
Signal
quality [%]
0
63(max)
Flywheel
counter
0
1
synch
0
1
data_ok
0
1.)
2.)
3.)
time
time
time
time
bne
interrupt
time
Within group and block synchronization control block a 6 bit (64 states) flywheel counter is
implemented to control RDS synchronization. After reset or a forced resynchronization by
setting “ar_res” bit rds_int[5], this counter increments from zero to one, if a valid RDS block
was detected. Valid means the syndrome has to be zero (“synz” = 1 rds_qu[0]) without any
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