S5T8701
FLEX TM ROAMING DECODER II
Synthesizer
Programming Control
Receiver
Host
Microprocessor
User
Interface
Receiver
Audio
Control
38.4kHz Clock
10pF
EXTS1
EXTS0
Audio to
Digital
Converter
S5T8701
LOBAT
Low Battery
Detector
10pF
Figure 2 : Example Block Diagram Using External Demodulator
The S5T8701 can also be configured to connect to a receiver capable of converting a 4 level audio signal into a 2
bit digital signal. In this mode, the S5T8701 has a 8 receiver control lines used for warming up and shutting down
a receiver in stages. It also includes configuration setting for the two post detection filter bandwidths required to
decode the two symbol rates of the FLEX signal. Also when using an external demodulator, the oscillator
frequency (or external clock) must be 76.8kHz and the CLKOUT signal (when enabled) is 38.4kHz clock output
capable of driving other devices.
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