DP83867IS: Please explain the difference between resets.

Hello JH, 

Thank you for the query.

For the hardware reset to work, you will have to ensure you follow the minimum reset time of ~1us. If you have a capacitor on the reset signal, the timing has to be taken care accordingly. The  IEEE software clears all the standard registers and not the extended registers.. 

8.5.5 Reset Operation

The DP83867 includes an internal power-on-reset (POR) function and therefore does not need to be explicitly reset for normal operation after power up. If required during normal operation, the device can be reset by a hardware or software reset.

8.5.5.1 Hardware Reset A hardware reset is accomplished by applying a low pulse, with a duration of at least 1 μs, to the RESET_N pin. This resets the device such that all registers are reinitialized to default values and the hardware configuration values are re-latched into the device (similar to the power up or reset operation).

8.5.5.2 IEEE Software Reset An IEEE registers software reset is accomplished by setting the reset bit (bit 15) of the BMCR register (address 0x0000). This bit resets the IEEE-defined standard registers.

8.5.5.3 Global Software Reset A global software reset is accomplished by setting bit 15 of register CTRL (address 0x001F) to 1. This bit resets all the internal circuits in the PHY including IEEE-defined registers and all the extended registers. The global software reset resets the device such that all registers are reset to default values and the hardware configuration values are maintained.

8.5.5.4 Global Software Restart A global software restart is accomplished by setting bit 14 of register CTRL (0x001F) to 1. This action resets all the PHY circuits except the registers in the Register File.

Regards,

Sreenivasa