SI4706-C31 Datasheet, PDF (24/36 Pages) Silicon Laboratories – HIGH-PERFORMANCE FM RDS/RBDS RECEIVER

Si4706-C31
4.14. Reference Clock
4.15. Control Interface
The Si4706 reference clock is programmable,
supporting RCLK frequencies in Table 10. Refer to
Table 3, “DC Characteristics” on page 5 for switching
voltage levels and Table 10, “Reference Clock and
Crystal Characteristics” on page 14 for frequency
tolerance information.
An onboard crystal oscillator is available to generate the
32.768 kHz reference when an external crystal and load
capacitors are provided. Refer to "2. Typical Application
Schematic" on page 15. This mode is enabled using the
POWER_UP command. Refer to Refer to “AN332:
Si47xx Programming Guide” and “AN344: Si4706/07/4x
Programming Guide.”
The Si4706 performance may be affected by data
activity on the SDIO bus when using the integrated
internal oscillator. SDIO activity results from polling the
tuner for status or communicating with other devices
that share the SDIO bus. If there is SDIO bus activity
while the Si4706 is performing the seek/tune function,
the crystal oscillator may experience jitter, which may
result in mistunes, false stops, and/or lower SNR.
A serial port slave interface is provided, which allows an
external controller to send commands to the Si4706 and
receive responses from the device. The serial port can
operate in three bus modes: 2-wire mode, 3-wire mode,
or SPI mode. The Si4706 selects the bus mode by
sampling the state of the GPO1 and GPO2 pins on the
rising edge of RST. The GPO1 pin includes an internal
pull-up resistor, which is connected while RST is low,
and the GPO2 pin includes an internal pull-down
resistor, which is connected while RST is low.
Therefore, it is only necessary for the user to actively
drive pins which differ from these states. See Table 11.
Table 11. Bus Mode Select on Rising Edge of
RST
Bus Mode
2-Wire
SPI
3-Wire
GPO1
1
1
0 (must drive)
GPO2
0
1 (must drive)
0
For best seek/tune results, Silicon Laboratories
recommends that all SDIO data traffic be suspended
during Si4706 seek and tune operations. This is
achieved by keeping the bus quiet for all other devices
on the bus, and delaying tuner polling until the tune or
seek operation is complete. The seek/tune complete
(STC) interrupt should be used instead of polling to
determine when a seek/tune operation is complete.
After the rising edge of RST, the pins GPO1 and GPO2
are used as general purpose output (O) pins as
described in Section “4.16. GPO Outputs”. In any bus
mode, commands may only be sent after V_IO and V_DD
supplies are applied.
In any bus mode, before sending a command or reading
a response, the user must first read the status byte to
ensure that the device is ready (CTS bit is high).
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Rev. 1.0