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RDS Control
1. Signal Flow (Refer to Block Diagram)
;
Picks up RDS signal from the output.of FM IF IC (1C403/LA1862M) through C302 (100P). Inputs this signal to RDS decoder IC301
(SAA6579T) for decoding, further, inputs this signal to synchro correction IC 1C302 (LC7074NM) to demodulate RDS data, thus
RDS data will be demodulated.
RDS data as in form of serial data consists of RDS START, RDS CLK, and RDS DATA is emitted from C302 and applied to system
control microcomputer IC901 (4PD78056).
This !C901 performs DCT-950R related all controls of LCD indication, control of CD
changer, etc. besides contro! of RDS. RDS data will be memorized in internal RAM of 1C901 and in IC903 (LC3517AML) of external
RAM.
2.
PS Function: Program Service Name
A function to indicate a name of broadcast station being received on the LCD by PS code in BLOCK 4 of Group OA. Also, functions
to indicate on the LCD when PS code is received through the continual check of PS code without relying on "AF/PTY" key or "TA"
key if it is FM BAND.
3. AF Function: Alternative Frequencies (frequency list of stations broadcasting the same program)
An automatic searching function, i.e. when reception condition of RDS station being received becomes poor for some reason, or in
case a station being received comes into out of service area and makes no reception as receiving is carried out on the moving
vehicle, shifts to a station broadcasting the same program. The automatic searching function only performs at the time "AF/PTY"
key ON or "TA" key ON state, on the other hand PI code or AF code is continually checked in FM BAND.
4. TAFunction: Traffic Announcement
Afunction at the time TA code of 12th bit in BLOCK 2 of group OA becomes ON, it automatically shifts the voice to RADIO and listen
to traffic announcement even if the voice of cassette or CD changer is in output state. At the same time, sound volume will also be
boosted however the volume is set at minimum that can be feasible to listen to the traffic announcement.
Note that TA function is
al
only effective in "TA" key ON state.
:
5. CT Function (Clock time)
;
CT-code is transmitted using Group 4A. CT-code is generally sent from broadcast station one time per one minute.
When receiving RDS broadcast transmitting CT-code, clock can be automatically adjusted by pressing "CLK" key for 2 seconds.
6. Search Function
1) AF Search
AF search performs automatic search as mentioned in "Paragraph 3. AF Function", also performs the optimum reception searching
(to select best receiving condition station among the same PI code broadcast stations) at the time RADIO ON, shifting from AM,
to FM BAND, or at preset call, etc.
The latter one is called AF Search (A) and the former one is called AF Search (B).
AF search (B) will function when field strength has reached less than certain level (this level is adjustable by VR 404, or RDS data
is unable to receive for 10 seconds (*), or the same PI code is unable to receive for 10 seconds.
Also, AF search (B) stops
searching when RDS code is enable to receive and at the time searches the same PI code station, then shifts the receiving station.
The both AF search (A) and (B) return to the receiving station searching has started when an appropriate station which satisfies
the conditions is unable to find in one round search.
AF Search (A
AF Search (B)
Ts
(**) For U.S.A. model, PI search cannot be performed in this case.
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