Silicon Laboratories SI4734/35-B20 - Manual (Page 26)

S i 4 7 3 4 / 3 5 - B 2 0
26 Rev. 1.0
will be ignored by the device if the transaction is
aborted.
For details on timing specifications and diagrams, refer
to Figure 6 and Figure 7 on page 10.
4.17. GPO Outputs
The Si4734/35 provides five general-purpose output
pins. The GPO pins can be configured to output a
constant low, constant high, or high-impedance. The
GPO pins can be reconfigured as specialized functions.
GPO2/INT can be configured to provide interrupts and
GPO3 can be configured to provide external crystal
support or as DCLK in digital audio output mode. In
digital output mode (Si4735 only), GPO6 and GPO7 can
be configured as DFS and DOUT respectively.
4.18. Firmware Upgrades
The Si4734/35 contains on-chip program RAM to
accommodate minor changes to the firmware. This
allows Silicon Labs to provide future firmware updates
to optimize the characteristics of new radio designs and
those already deployed in the field.
4.19. Reset, Power Up, and Power Down
Setting the RST pin low will disable analog and digital
circuitry, reset the registers to their default settings, and
disable the bus. Setting the RST pin high will bring the
device out of reset.
A power down mode is available to reduce power
consumption when the part is idle. Putting the device in
power down mode will disable analog and digital
circuitry while keeping the bus active.
4.20. Programming with Commands
To ease development time and offer maximum
customization, the Si4734/35 provides a simple yet
powerful software interface to program the receiver. The
device is programmed using commands, arguments,
properties and responses.
To perform an action, the user writes a command byte
and associated arguments, causing the chip to execute
the given command. Commands control an action such
as power up the device, shut down the device, or tune
to a station. Arguments are specific to a given command
and are used to modify the command. A complete list of
commands is available in Table 14, “Si473x Command
Summary,” on page 27.
Properties are a special command argument used to
modify the default chip operation and are generally
configured immediately after power up. Examples of
properties are de-emphasis level, RSSI seek threshold,
and soft mute attenuation threshold. A complete list of
properties is available in Table 15, “Si473x Property
Summary,” on page 28.
Responses provide the user information and are
echoed after a command and associated arguments are
issued. All commands provide a one-byte status update
indicating interrupt and clear-to-send status information.
For a detailed description of the commands and
properties for the Si4734/35, see “AN332: Universal
Programming Guide.”