SPRADN4B October 2024 – September 2025 AM62P , AM62P-Q1
A 3-input ANDing logic can be used to implement the attached device (EPHY) reset. Processor GPIO (used to locally reset the EPHY) is connected as one of the input to the ANDing logic AND gate with provision for pullup (10kΩ or 47kΩ) (to support boot) near to the ANDing logic AND gate input and provision for 0Ω to isolate the GPIO output for testing or debug. The other two inputs to the AND gate are the MAIN domain POR (cold reset) status output (PORz_OUT) and MAIN domain warm reset status output (RESETSTATz).
In case a dual input ANDing logic is considered PORz_OUT (pin strapping on power-up) or RESETSTATz can be connected as one of the input with the processor GPIO input connected as the other (second) input. When more than one (x2) EPHy are used, the recommendation is to provide provision to reset the EPHy individually.
A pullup or pulldown (10kΩ) at the output of the ANDing logic can be used based on the EPHY reset input polarity. The EPHY is required to be held in reset for a specified minimum time after the clock is valid.
In case the processor MAIN domain warm reset status output (RESETSTATz) is directly used to reset the EPHY (attached device), the recommendation is to match the IO voltage level of RESETSTATz with the attached device. A level translator is recommended to match the IO level. A resistor divider can be used alternatively for level shifting, provided optimum value of the resistor divider is selected. If too high the rise/fall time of the EPHY reset input can be slow and introduce too much delay. Use of too low value resistors as divider causes the processor to source too much steady-state current during normal operation.