TDA7529 Datasheet, PDF (29/60 Pages) STMicroelectronics – RF front-end for AM/FM DSP car-radio with IF sampling

TDA7529
5
Tuning state machine
Tuning state machine
Frequency changes in a system employing the TDA7529 can be efficiently performed using
a built-in state machine which simplifies the microprocessor supervisory functions. The state
machine, which can work in 8 different modes, can be invoked by a simple WRITE operation
into the tuner registers and, provided that the frequency to be jumped to has been pre-
loaded into the front-end registers through a previous separate or is loaded through a
concurrent WRITE operation, the FE jump sequence is automatically managed and flags
are provided to the back-end to indicate the current condition.
5.1
5.1.1
5.1.2
Tuning state machine modes
Hereafter the description of the 8 modes can be found. They are chosen by Byte 12
bits<6:4>.
The diagrams depicting the FE and flag conditions for each of the 8 modes are as follows:
Mode 000: buffer (nil)
When this mode is selected, no action is undertaken by the state machine.
Mode 001: preset
Figure 8.
EVENTS
Preset timing diagram
bus
STOP
event
regs
swap
TIME
transmission with subaddr. bit 7 = 1 wait T1ms
AFSAMPLE
wait for Tplllock
wait 50 us
wait T60ms
AFHOLD
B.E. OPERATION
mute audio
quality dets in fast mode
unmute audio
AC00045
This mode is used to jump to a different frequency and stay there, with reception at the end
of the sequence.
AFSAMPLE can be used to tell the back-end when to mute and to unmute the audio output.
The 60 ms mute time (programmable) after the PLL has reached the locked condition can
be used to check the RDS signal presence and content in addition to the analog quality
information.
AFHOLD can be used to tell the back-end to switch to faster time constants for quick quality
acquisition.
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