tea5766uk NXP Semiconductors, tea5766uk Datasheet - Page 11

• Manufacturer Part Number: tea5766uk
• Description: Tea5766uk Stereo Fm Radio + Rds
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA5766UK_1
Product data sheet
7.19 RDS/RBDS decoder
7.20 Auto search and preset mode
The RDS decoder provides block synchronization, error correction and flywheel function
for reliable extraction of RDS or RBDS block data. Different modes of operation can be
selected to fit different application requirements. Availability of new data is signalled by bit
DAVFLG and output pin INTX, which generates an interrupt. Up to two blocks of data and
status information are available via the I
The behavior of the DAVFLG is described in
In search mode TEA5766UK can search channels automatically.
When the INTX signal is used as an interrupt to the host processor to indicate a search
stop, the INTMSK register must be reset and only bit FRRMSK must be set. In this way
the host processor will only be interrupted when the search/preset algorithm is ready.
Search mode is initiated setting the SM bit to logic 1 in the FRQSET register. When bit
SUD is logic 0 then it searches down and when SUD is logic 1 it searches up. The tuner
starts searching at the frequency where it is or at a new start frequency programmed to
the tuner. With the Search Stop Level (SSL[1:0]) bits the minimum field strength of
channels to be found can be set. The tuner will stop on a channel with a field strength
equal to or higher than this reference level and then will check the IF frequency. When
both are valid the search mode stops. If the level check or the IF count fails, it continues
the search. When no channels are found the TEA5766UK stops searching when it has
reached the band-limit and bit BLFLAG goes to logic 1. A search always stops with bit
FRRFLAG being set and a hardware interrupt.
After this interrupt the TEA5766UK will keep its status and will not update the INTREG,
FRQCHK and TUNCHK tuner registers for a period of 15.6 ms. The state of the
TEA5766UK can be checked by reading tuning registers: INTREG, FRQCHK and
TUNCHK.
A preset is done by setting bit SM to logic 0 and writing a frequency to byte FRQSETMSB.
The tuner jumps to the selected frequency and sets bit FRRFLAG when it is ready. After
this interrupt the TEA5766UK will keep not update the tuner registers for a period of
15.6 ms. The state of the TEA5766UK can be checked by reading registers: INTFLAG,
FRQCHK and TNCTRL.
Table 5.
Bit
IFFLAG
0
0
0
0
1
Table 5
Tuner truth table
BLFLAG
0
0
1
1
0
shows the possible states after an auto search or a preset.
Rev. 01 — 22 March 2007
FRRFLAG
0
1
0
1
0
Table 5
[1]
shows the possible states after an auto search or preset.
Comment
this cannot occur if INTX has gone LOW and only IFMSK,
FRRMSK and BLMSK were set
channel found during search/preset FRRMSK set
not a valid state
a valid channel found and the band limit has been reached
during a search; BLMSK or FRRMSK set
not a valid state
2
C-bus in a single transmission.
Section
Figure 4
9.
shows this procedure.
TEA5766UK
Stereo FM radio + RDS
© NXP B.V. 2007. All rights reserved.
10 of 59