[FAQ] TPS23861: How to configure TPS23861 in different operating modes? What’s the AUTO Bit?

Register 0x11 is used to configure operating modes for TPS23861. AUTO Bit is the MSB of register 0x11(register 0x11’s value is stored in the EEPROM and will not be changed after POR).  AUTO Bit determines some registers’ default value after power on reset. For example, the default value of register 0x12 is “0xAAAAAAAAb”. “A” represents the AUTO Bit value, 0 or 1.  If the AUTO Bit is set to 1, register 0x12’s default value is “0x11111111b” which means all ports are set to Auto Mode. Otherwise, the default value of 0x12 after POR is “0x00000000b” which set all ports to Off Mode. Generally, if autonomous mode is used (without host control), the AUTO Bit should be set to 1; if Semi-Auto or Manual Mode is used (with host control), the AUTO Bit should be cleared. Otherwise, if the communication is not built up successfully, the device will go back to Auto Mode after POR even the operating mode was set to Semi-Auto or Manual Mode.  The AUTO Bit is set to 1 by default when the device is shipped.

 Additional Resources

• Check out TI's PoE landing page: www.TI.com/PoE

• Learn about the IEEE802.3bt standard: Power over Ethernet: Getting Started with the New Standard