Signal path isolation for conductive circuit paths and multipurpose interfaces

Abstract

A device can be configured to provide isolation between conductive circuit paths and to selectively connect one of the conductive circuit paths to a shared interface. Each conductive circuit path can include driver circuitry designed to transmit signals according to a particular protocol and a corresponding signal speed. The shared interface can be, in one instance, a connector designed for connection to other devices. The other devices can be configured to communicate over the shared interface using one or more of the particular protocols provided using the different circuit paths.

What is claimed is: 
     
         1 . A device for reducing loading on a prioritized conductive signal circuit path that share a multipurpose signal interface which passes conductively-carried signals received from respective ones of the conductive signal circuit paths to facilitate the use of different protocols for communication in each path, the device comprising:
 a first conductive signal circuit path configured and arranged to transmit an electrical data signal at a signal speed designed for use with a first protocol;   a second conductive signal circuit path configured and arranged to transmit an electrical data signal at a signal speed designed for use with a second protocol and that is slower relative to the signal speed designed for use with the first protocol;   a third conductive signal circuit path configured and arranged to transmit an electrical data signal at a speed designed for use with a third protocol and that is slower relative to the signal speed designed for use with the first protocol;   a first multiplexer circuit configured and arranged to transmit a signal on a first output conductive signal circuit path by selecting, in response to a first control bit, between the second conductive signal circuit path and the third conductive signal circuit path and by electrically isolating the other of the second conductive signal circuit path and the third conductive signal circuit path from the first output conductive signal circuit path;   a second multiplexer circuit configured and arranged to transmit a signal on a second output conductive signal circuit path by selecting, in response to a second control bit, between the first conductive signal circuit path and the first output conductive signal circuit path; and   control circuitry configured and arranged to generate the first and second control bits in response to a selection of one of the first, second and third protocols for use of the multipurpose signal interface.   
     
     
         2 . The device of  claim 1 , wherein the second multiplexer circuit is further configured and arranged to wire-OR the first conductive signal circuit path and the first output conductive signal circuit path in response to the control bit indicating that the first conductive signal circuit path is selected. 
     
     
         3 . The device of  claim 1 , wherein the second output conductive signal circuit path is electrically connected by a conductive trace to a multipurpose connector designed to connect to another device operating according to any of the first, second and third protocols and wherein the signal speed is one of a signal transition rate and an signal edge transition speed. 
     
     
         4 . The device of  claim 1 , wherein the signal speed designed for use with the first protocol is between 1 GHz and 100 GHz and the speed designed for use with the second protocol is between 1 KHz and 1 MHz. 
     
     
         5 . The device of  claim 1 , wherein the second and third protocols include one of Display Data Channel (DDC) and/or Inter-Integrated Circuit (I 2 C). 
     
     
         6 . The device of  claim 1 , wherein the first protocol includes one of Serial Peripheral Interface Bus (SPI) with Universal Serial Bus (USB), DisplayPort and Thunderbolt. 
     
     
         7 . The device of  claim 1 , further including a third multiplexer circuit configured and arranged to generate a third output conductive signal circuit path by selectively passing signals from one of a fourth conductive signal circuit path and a fifth conductive signal circuit path and to electrically isolate the other of the fourth conductive signal circuit path and the fifth conductive signal circuit path from the third conductive output signal circuit path, wherein the fourth conductive signal circuit path and the fifth conductive signal circuit path are each configured and arranged to carry electrical signals transmitted according to protocols that have a slower signal speed relative to the first protocol. 
     
     
         8 . The device of  claim 1 , wherein the second multiplexer circuit is further configured and arranged to selectively pass signals from a fourth conductive signal circuit path that operates at a signal speed that is greater than the signal speed of the second protocol. 
     
     
         9 . The device of  claim 1 , wherein one or more of the conductive signal circuit paths are differential conductive signal circuit paths. 
     
     
         10 . The device of  claim 1 , further including bias circuitry configured and arranged to provide signal bias to the first output conductive signal circuit path. 
     
     
         11 . The device of  claim 1 , wherein each multiplexer is configured and arranged to use a single level of transistors to effect the transmission of a signal on the respective and corresponding output conductive signal circuit path. 
     
     
         12 . A method for reducing high-speed loading between conductive signal circuit paths that share a multipurpose signal interface which passes conductively-carried signals received from respective ones of the conductive signal circuit paths to facilitate the use of different protocols for communication in each path, the method comprising:
 transmitting an electrical data signal, at a signal speed designed for use with a first protocol and on a first conductive signal circuit path;   transmitting an electrical data signal, at a signal speed designed for use with a second protocol and that is slower relative to the signal speed designed for use with the first protocol, on a second conductive signal circuit path;   transmitting an electrical data signal, at a speed designed for use with a third protocol and that is slower relative to the signal speed designed for use with the first protocol, on a third conductive signal circuit path;   transmitting, using a first multiplexer circuit, a signal on a first output conductive signal circuit path by selecting, in response to a first control bit, between the second conductive signal circuit path and the third conductive signal circuit path and by electrically isolating the other of the second conductive signal circuit path and the third conductive signal circuit path from the first output conductive signal circuit path;   transmitting, using a second multiplexer circuit, a signal on a second output conductive signal circuit path by selecting, in response to a second control bit, between the first conductive signal circuit path and the first output conductive signal circuit path; and   generating, using control circuitry, the first and second control bits in response to a selection of one of the first, second and third protocols for use of the multipurpose signal interface.   
     
     
         13 . The method of  claim 12 , further including a step of transmitting, using the second multiplexer circuit and in response to the second control bit indicating a selection of the first conductive signal circuit path, a signal on a second output conductive signal circuit path that is a wire ORing of the first conductive signal circuit path and the first output conductive signal circuit path. 
     
     
         14 . The method of  claim 12 , wherein the first protocol includes one of Serial Peripheral Interface Bus (SPI) with Universal Serial Bus (USB), DisplayPort and Thunderbolt. 
     
     
         15 . The method of  claim 12 , wherein the second protocol includes one of Display Data Channel (DDC) and/or Inter-Integrated Circuit (I 2 C). 
     
     
         16 . The method of  claim 12 , further including a step of providing bias to the first output conductive signal circuit path to prevent voltage drift. 
     
     
         17 . The method of  claim 12 , further including a step of detecting a protocol used by a device connected to the multipurpose signal interface and wherein the step of generating control bits is responsive to the detection of the protocol used by the connected device. 
     
     
         18 . The method of  claim 12 , further including the steps of detecting a protocol used by a device connected to the multipurpose signal interface and enabling and disabling signal conditioning circuitry in response to the detection of the protocol used by the connected device.