Abstract:
An interface between two or more integrated circuit devices employs isolation techniques to provide electrical isolation of a digital signal for transmission of the digital signal between a master device and one or more slave devices. Unidirectional isolator channels are utilized to transmit bidirectional digital signals, and a selection of an isolator channel operating in an intended direction is performed by direction control logic. Logic that monitors read and write transactions operates to determine a desired direction of the digital signal and accordingly directs the digital signal through an appropriate isolator channel.

Description:
BACKGROUND 
       [0001]    Isolation of digital signals communicated between devices is needed to reduce safety hazards as well as for noise robustness factors. Shock and fire hazards may result from digital signals that are not isolated. Additionally, excess noise may be introduced into the digital signals as a result of insufficient isolation. Thus, electrical isolation of digital signals being transmitted between devices, while still allowing the digital signal to be transmitted across an interface between the devices, is a necessary requirement. 
         [0002]    Interface components, operating to communicate digital signals between devices, may be utilized to isolate the digital signals. Isolator channels are components for electrically isolating digital signals and may be employed in interface components for such a purpose. Isolator channels are uni-directional components, while digital signals may be bi-directional. Thus, one isolator channel may be utilized to transmit a digital signal in one direction, while a second isolator channel is needed to transmit the digital signal in an opposite direction. For example, the first isolator channel may be used for communication from a transmitter to a receiver, while the second isolator channel may be used for communication from the receiver to the transmitter. 
         [0003]    When a digital signal reaches an interface between devices, it is necessary to determine the intended direction of the signal to allow for an isolator channel operating in the intended direction to be utilized to electrically isolate the digital signal. Thus, a need exists for a process and component to manage and control the direction of the signal across the interface. 
       SUMMARY 
       [0004]    A digital signal, such as a management data input/output (MDIO) signal, is communicated between two or more devices, such as microprocessors or peripheral devices, across an interface. The interface operates to receive, isolate, and transmit the digital signal. Isolator channels or isolation techniques are employed at the interface to electrically isolate the devices while still allowing the transmission of the digital signal. The isolator channels or isolation techniques are managed by direction control logic, to control the direction of the signal across the interface. Read and write transactions between master and slave devices may be monitored to direct the signal across an appropriate isolation channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The foregoing summary and the following detailed description are better understood when read in conjunction with the appended drawings. Exemplary embodiments are shown in the drawings; however, it is understood that the embodiments are not limited to the specific methods and instrumentalities depicted herein. In the drawings: 
           [0006]      FIG. 1  is a diagram illustrating an exemplary MDIO isolator component; 
           [0007]      FIG. 2  is a flowchart illustrating an additional exemplary method of communicating a digital signal across an interface; 
           [0008]      FIG. 3  is a timing diagram illustrating an exemplary frame of a digital signal communicated across an interface between two devices; and 
           [0009]      FIG. 4  is an additional timing diagram illustrating another exemplary frame of a digital signal communicated across an interface between two devices. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    With reference to  FIG. 1 , a diagram illustrating an exemplary MDIO isolator component  100  for isolating bi-directional digital signals is shown. This exemplary component may be utilized in MDIO applications in which a digital signal is communicated between one of a plurality of slave devices  150   a - 150   n  and a master device  140 . The MDIO isolator component  100  may be utilized as an interface between a microprocessor and one or more peripheral chips, between two master peripheral chips, or between any components used for exchange of digital data. 
         [0011]    The MDIO isolator component  100  may operate to communicate and electrically isolate a digital signal between two or more devices, such as master device  140  and slave devices  150   a - 150   n.  Bi-directional communication ports  110   a  and  110   b  may act as the link between the master device  140  and slave devices  150   a - 150   n  and the MDIO isolator component  100 . The bi-directional communication ports  110   a  and  110   b  may operate to transmit and receive the digital signal between the devices  140  and  150   a - 150   n.  The digital signal may be a MDIO signal, a serial clock signal, or a serial data signal, for example. Other types of digital signals may be communicated between the devices  140  and  150   a - 150   n  across the MDIO isolator component  100 . Moreover, the MDIO isolator component  100  may include additional bidirectional communication ports. Two ports,  110   a  and  110   b,  are shown only as an exemplary embodiment, as illustrated in  FIG. 1 . 
         [0012]    The MDIO isolator component  100  includes one or more isolator channels  130  for providing electrical isolation between the devices  140  and  150   a - 150   n.  Four isolator channels  130   a - 130   d  are shown in the exemplary embodiment illustrated in  FIG. 1 ; however, additional or fewer isolator channels  130  may be used. Isolator channels  130   a - 130   d  may be uni-directional isolator channels that operate to provide high-volt electrical isolation to digital signals. As the isolator channels  130   a - 130   d  are uni-directional components, the digital signals may be bi-directional. Thus, one isolator channel  130   a - 130   d  may be utilized to transmit a digital signal in one direction, while a second isolator channel  130   a - 130   d  is needed to transmit the digital signal in an opposite direction. The means of isolation may be, but are not limited to, capacitive, magnetic, optical, or acoustical means. 
         [0013]    In an exemplary embodiment, a default state may include a transmission of a digital signal from the master device  140  to the slave devices  150   a - 150   n.  The default state may be referred to as a write cycle. In the default state, the digital signal may be directly transmitted to an isolator channel  130   a - 130   d  for isolation of the digital signal. The isolated digital signal may then be transmitted to one or more of the slave devices  150   a - 150   n.    
         [0014]    However, when a digital signal needs to be sent to the master device  140 , a read cycle occurs. In this instance, direction detection/control logic  120  may be used to determine an intended transmission direction of the digital signal. Direction detection/control logic  120  may also be utilized to transmit the digital signal over an isolator channel  130   a - 130   d  operating in the transmission direction. 
         [0015]    Direction detection/control logic  120  may operate to analyze the digital signal to determine an occurrence of a read transaction. Such an occurrence may indicate that the digital signal is being transmitted to the master device  140  from one of the slave devices  150   a - 150   n.  The occurrence also indicates that the isolator channel  130   a - 130   d  may need to operate in the direction from the slave devices  150   a - 150   n  to the master device  140 . 
         [0016]    For example, direction detection/control logic  120 , upon monitoring the data stream between the devices  140  and  150   a - 150   n,  detects a read cycle. The digital signal is transmitted through one of the isolator channels  130   a - 130   d  operating to isolate the digital signal in the direction from the slave devices  150   a - 150   n  to the master device  140 . After electrical isolation, the digital signal may be transmitted to the master device  140 . 
         [0017]      FIG. 2  is a flowchart illustrating an exemplary method of communicating a digital signal across a MDIO isolator component  100 . In the exemplary method, digital signal transmission occurs between a master device  140  and a plurality of slave devices  150   a - 150   n  of  FIG. 1 . 
         [0018]    At  210 , a digital signal is received from one of devices  140  or  150   a - 150   n.  At  220 , the digital signal is analyzed to determine an occurrence of a read transaction. The analysis to determine a read transaction occurrence may include analyzing the bits of the digital signal to determine a read transaction. 
         [0019]    At  230 , upon determination of a read transaction occurrence, the digital signal is transmitted through an isolation channel  130  from one of the slave devices  150   a - 150   n  to the master device  140 . At  240 , the master device  140  receives the digital signal that has been electrically isolated by the isolation channel  130 . 
         [0020]    At  250 , after a predefined number of bits of the isolated digital signal are transmitted, a subsequent digital signal may be communicated from the master device  140 , through an isolation channel  130   a - 130   d  operating in the transmission direction, to one or more of the plurality of slave devices  150   a - 150   n.    
         [0021]    At  260 , the digital signal is further analyzed to determine a completion of the read transaction from one of the devices  150   a - 150   n.  The determination of the read transaction completion may be performed by the direction detection/control logic  120  by analyzing the bits of the digital signal. A 16-bit read field sent by the MDIO slave device  150   a - 150   n  may mark the completion of the read transaction. 
         [0022]    After the read transaction is complete, the default state may resume, where digital signals are transmitted from the master device  140  during write cycles to the plurality of slave devices  150   a - 150   n.  At  270  a subsequent digital signal is thus transmitted through the isolation channel  130  from the master device  140 . At  280 , the isolated, subsequent digital signal is transmitted to one or more of the plurality of slave devices  150   a - 50   n.    
         [0023]      FIG. 3  is a timing diagram illustrating an exemplary frame of the digital signal being communicated across the MDIO isolator component  100  of  FIG. 1 . The exemplary frame illustrates a write cycle, in which the master device  140  is transmitting the digital signal to one or more of the slave devices  150   a - 150   n.  The direction detection/control logic  120  examines the OPI and OPO bits to determine the direction of the digital signal. In the case of a write transaction, as shown in  FIG. 3 , the direction detection/control logic  120  assumes the default state of transmitting the digital signal from the master device  140  to one or more of the slave devices  150   a - 150   n  after isolating the digital signal through one of the isolator channels  130   a - 130   d  operating in the transmission direction. 
         [0024]      FIG. 4  is an additional timing diagram illustrating another exemplary frame of the digital signal being communicated across the MDIO isolator component  100  of  FIG. 1 . The exemplary frame illustrates a read cycle, in which one of the slave devices  150   a - 150   n  is transmitting the digital signal to the master device  140 . Again, the direction detection/control logic  120  examines the OPI and OPO bits to determine the direction of the digital signal. Upon determination of a read transaction, as illustrated in  FIG. 4 , the direction detection/control logic  120  utilizes one of the isolator channels  130   a - 130   d  operating in the direction from the slave devices  150   a - 150   n  to the master device  140 . The read transaction is complete after the transmission of the 16-bit read field. 
         [0025]    The foregoing examples are provided merely for the purpose of explanation and are in no way to be construed as limiting. While reference to various embodiments are shown, the words used herein are words of description and illustration, rather than words of limitation. Further, although reference to particular means, materials, and embodiments are shown, there is no limitation to the particulars disclosed herein. Rather, the embodiments extend to all functionally equivalent structures, methods, and uses, such as are within the scope of the appended claims.