PD17012GF-055_15 Datasheet, PDF (41/84 Pages) Renesas Technology Corp – SINGLE-CHIP MICROCONTROLLER WITH ON-CHIP PRESCALER, PLL FREQUENCY SYNTHESIZER, AND IF COUNTER FOR CAR-MOUNTED FM/MW/LW RADIO

µPD17012GF-055
(2) AF check
Data of the AF operation memory is used for AF checking. One station is checked at a time.
1 AF check start condition:
The electric field strength of the broadcast being received is divided into the following three stages
(the numeric values are those when the read A/D values are 0-3FH) by the voltage which is input
from SD pin.
L < 0CH < M ≤ 20H ≤ H
SD Level
H
M
L
Description of Operations
AF check not started.
AF check started on a station every 5 seconds.
All the AFs at the time checked at once.
2 AF check stop condition:
AF checking is stopped when the SD level of the AF-checked broadcast is higher than that of the
broadcast originally being listened to, and the PI of the broadcast at the check destination has
satisfied the STOP condition.
Conditions for broadcast (PI) capable of AF switchover are as follows:
• Broadcast whose 16 bits are completely identical, including the PI code and the area cover code
of the broadcast being currently received.
• Broadcast whose area cover code is ‘4’ to ‘F’ when the PI code and the area cover code of the
broadcast being currently received is ‘1’ to ‘3’, and whose remaining 12 bits are identical.
• Broadcast whose area cover code is ‘1’ to ‘3’ when the PI code and the area cover code of the
broadcast being currently received is ‘4’ to ‘F’, and whose remaining 12 bits are identical.
3 AF check for calling when CE low level has been switched over to high level or when the
last station is an FM RDS station:
AF checking is performed for calling when the CE low level has been switched over to low level or
when the last station is an FM RDS station.
At this time, the AF data of the last channel memory is moved to the AF operation memory, and
immediately all the AFs are checked. The broadcasting station whose PI stored in the preset memory
has satisfied the STOP condition and whose SD level is the highest is selected for reception. This
AF checking is performed during MUTE output.
If no station satisfies the STOP condition as a result of checking the broadcast stations of the preset
frequency and all their AF, the SEEK operation is performed upwards from the preset frequency to
detect the broadcasting station which satisfies the STOP condition.
If a broadcasting station which satisfies the STOP condition appears, the SEEK operation is halted
to receive the relevant broadcasting station (PI search). Even if the SEEK operation is carried out
across the entire width of reception band, if a broadcasting station which satisfies the STOP condition
cannot be found, the SEEK operation is halted to receive the originally set frequency.
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