Silicon Laboratories SI4734/35-B20 GPO Outputs, Firmware Upgrades, Programming with Commands

Si4734/35-B20

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.”

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