3.6 Pin Configuration

Some pins of the LAN8670/1/2 may take on multiple functions depending on the device and mode. The functionality of five pins of the LAN8670 varies depending upon the device mode set by the MODE[1:0] Configuration Straps. Table   1 shows the functionality assigned to these pins based on the configured device mode.

The GPIO0 pin is a multipurpose pin that can be configured as desired for multiple uses. This feature is useful for enabling specific features that would not otherwise be available for a specific device package or configuration. For example, Time Sensitive Networking (TSN) is supported through the ability to assert output signals when packets matching a specific pattern are transmitted and/or received. The GPIO0 pin may be configured as a Transmit Packet Indication (TXPI), Receive Packet Indication (RXPI), or Receive/Transmit Packet Indication (RXTXPI) output, as needed. Additionally, GPIO0 may be configured as an Application Controlled Media Access (ACMA) input pin.

The GPIO0 pin functionality is configured by writing to the GPIO0 Signal Select (GPIO0SS) field of the Pin Control (PINCTRL) register. The GPIO0 Signal Select should be configured prior to configuring and enabling the underlying Packet Pattern Matching or Application Controlled Media Access blocks.

Valid configurations for the GPIO0 pin depend on the device in use and its operating mode. When a dedicated native pin is available, this pin must be used for the provided function rather than the GPIO0 pin. Table 3-14 below shows the valid configurations for the GPIO0 pin. When a pin number is shown, this is an invalid configuration for the GPIO0 Signal Select and the designated dedicated pin must be used instead.

Because the LAN8670 supports all operating modes, those being Media Independent Interface (MII), Single-Clock MII (SC-MII), and Reduced Media Independent Interface (RMII), it is important to know in which mode the device will be operated in. In MII mode, GPIO0 can be configured to any of the four possible functions. However, in SC-MII and RMII modes, it is limited to only be configured as TXPI or RXTXPI functionality.

For the LAN8671, GPIO0 may again fulfill any of the four possible configurations. To be noted here, the LAN8671 is only operated in RMII mode.

For the LAN8672, GPIO0 may again only be configured as TXPI or RXTXPI, since this device only operates in MII mode.