Ethernet interface and related systems methods and devices
Described is a digital interface and related systems, method and devices. In some embodiments an interface may be an interface between a link layer and a physical transmission medium. The interface may be configured for a bit rate and/or reference clock that limits electromagnetic emissions (EME), for example as compared to a bit rate and/or clock rate specified by interfaces widely used in industry.
1. A method, comprising:
generating a clock;
generating a divided clock responsive to the clock;
clocking, using the clock, a datapath of an Ethernet physical layer at a first clock rate;
clocking, using the divided clock, a first interface for operatively coupling the Ethernet physical layer with an Ethernet link layer, wherein clocking the first interface comprises clocking the first interface at a second clock rate that is substantially equal to a bit rate of the first interface; and
synchronizing the bit rate and the clock rate of the first interface with a bit rate and a clock rate of a second interface at the Ethernet link layer.
2. The method of claim 1 , wherein generating the clock at a first frequency comprises generating the clock at the first frequency at a crystal oscillator.
3. The method of claim 1 , wherein the second clock rate is substantially 5 megahertz and the first clock rate is substantially 25 megahertz.
4. The method of claim 1 , wherein the second clock rate is substantially 2.5 megahertz and the first clock rate is substantially 25 megahertz.
5. The method of claim 1 , further comprising crossing over from a first clock domain to a second clock domain at the datapath, wherein the first clock domain is associated with the first clock rate and the second clock domain is associated with the second clock rate.
6. The method of claim 1 , further comprising choosing the second clock rate of the first interface responsive to an electromagnetic emissions (EME) limit.
7. A system, comprising:
a datapath of an Ethernet physical layer, the datapath configured for a first clock rate;
a first interface for operatively coupling the Ethernet physical layer to an Ethernet link layer, the first interface configured for a second clock rate that is substantially equal to a bit rate of the first interface;
a clock generator configured to generate a clock for clocking the datapath and for clocking the first interface; and
a harmonizing layer of the Ethernet link layer, the harmonizing layer configured to synchronize the bit rate and the clock rate of the first interface with a bit rate and a clock rate of a second interface.
8. The system of claim 7 , wherein the datapath comprises a clock and data recovery circuitry.
9. The system of claim 7 , further comprising a clocking interface configured to provide a divided clock responsive to the clock.
10. The system of claim 9 , wherein the datapath is configured to cross over from a first clock domain to a second clock domain responsive to one or more control signals received from the clocking interface.
11. The system of claim 10 , wherein the first clock domain is associated with the first clock rate and the second clock domain is associated with the second clock rate.
12. The system of claim 7 , wherein the second clock rate is substantially 5 megahertz and the first clock rate is substantially 25 megahertz.
13. The system of claim 7 , wherein the second clock rate is substantially 2.5 megahertz and the first clock rate is substantially 25 megahertz.
14. The system of claim 7 , wherein the first interface comprises one or more outputs, and an output of the one or more outputs is assigned to a signal for non-exclusive collision avoidance signaling.