Transmit/receive unit, and methods and apparatus for transmitting signals between transmit/receive units

Abstract

In one embodiment, apparatus for transmitting and receiving data includes a transmission line network having at least three input/output terminals; at least three transmit/receive units, respectively coupled to the at least three input/output terminals; and a control system. The control system is configured to, depending on a desired direction of data flow over the transmission line network, i) dynamically place each of the transmit/receive units in a transmit mode or a receive mode, and ii) dynamically enable and disable an active termination of each transmit/receive unit. Methods for using this and other related apparatus to transmit and receive data over a transmission line network are also disclosed.

What is claimed is: 
     
         1 . A method for transmitting signals between at least three transmit/receive units coupled to a transmission line network, the method comprising:
 for each signal transmission over the transmission line network, designating one of the transmit/receive units as a transmitting unit and designating all other ones of the transmit/receive units as non-transmitting units,   for each of at least two different signal transmissions over the transmission line network,
 designating a different one of the transmit/receive units as the transmitting unit; 
 using at least one of the non-transmitting units, actively terminating the transmission line network by driving a DC voltage through an active driver of each of the at least one non-transmitting unit, the active driver having an output that is coupled to the transmission line network via a termination resistor; 
 from the transmitting unit, transmitting a signal over the transmission line network; and 
 receiving the transmitted signal at one or more of the non-transmitting units. 
   
     
     
         2 . The method of  claim 1 , further comprising, for each of the at least two different signal transmissions over the transmission line network:
 actively terminating the transmission line network by driving a DC voltage through an active driver of each non-transmitting unit coupled to the transmission line network.   
     
     
         3 . Apparatus for transmitting and receiving data, comprising:
 a transmission line network having at least three input/output terminals;   at least three transmit/receive units, respectively coupled to the at least three input/output terminals, each of the transmit/receive units having
 i) an active receiver having a receiver input coupled to a respective one of the input/output terminals; 
 ii) an active driver having a driver input coupled to a driver output; 
 iii) a termination resistor coupling the driver output to a respective one of the input/output terminals; and 
 iv) a switching element configured to selectively couple the driver input to a DC voltage source. 
   
     
     
         4 . The apparatus of  claim 3 , wherein the switching element is further configured to selectively couple the driver input to a signal source, the apparatus further comprising:
 a control system coupled to the switching elements of the at least three transmit/receive units, the control system configuring the switching elements of the transmit/receive units to A) couple the driver input and the signal source of a transmitting one of the transmit/receive units, and B) couple the driver input and DC voltage source of at least one non-transmitting one of the transmit/receive units.   
     
     
         5 . The apparatus of  claim 3 , wherein for each of the transmit/receive units, the switching element of the respective transmit/receive unit comprises:
 a multiplexer having first and second multiplexer inputs, a multiplexer output coupled to the driver input, and a select input; wherein the DC voltage source is coupled to the first multiplexer input and the signal source is coupled to the second multiplexer input.   
     
     
         6 . The apparatus of  claim 5 , further comprising:
 a control system coupled to the select inputs of the multiplexers, the control system configuring the multiplexers to A) couple the driver input and the signal source of a transmitting one of the transmit/receive units, and B) couple the driver input and the DC voltage source of other ones of the transmit/receive units.   
     
     
         7 . The apparatus of  claim 3 , wherein the at least three transmit/receive units consist of three transmit/receive units. 
     
     
         8 . The apparatus of  claim 3 , wherein the transmission line network comprises three transmission line segments, each of the transmission line segments having first and second ends, wherein the first ends of the transmission line segments are coupled to respective ones of the transmit/receive units, and wherein the second ends of the transmission line segments are coupled to one another at a common branching node. 
     
     
         9 . The apparatus of  claim 8 , wherein each of the three transmission lines has a characteristic impedance of 50 Ohms. 
     
     
         10 . The apparatus of  claim 3 , wherein the transmission line network defines a 1:2 signal fan-out from a first one of the transmit/receive units to second and third ones of the transmit/receive units. 
     
     
         11 . The apparatus of  claim 10 , further comprising:
 a first adjustable delay element coupled to a receiver output of the active receiver of the second transmit/receive unit;   a second adjustable delay element coupled to a receiver output of the active receiver of the third transmit/receive unit; and   a delay controller configured to adjust delays of the first and second adjustable delay elements.   
     
     
         12 . The apparatus of  claim 3 , wherein the active driver of a first one of the transmit/receive units is configured to transmit signals carrying timing and voltage information over the transmission line network, and wherein the transmission line network is configured to split the signals and provide the signals to second and third ones of the transmit/receive units. 
     
     
         13 . The apparatus of  claim 3 , wherein first and second ones of the transmit/receive units are configured to transmit signals carrying timing and voltage information over the transmission line network, and wherein the transmission line network is configured to provide the signals driven by the first and second ones of the transmit/receive units to a third one of the transmit/receive units. 
     
     
         14 . Apparatus for transmitting and receiving data, comprising:
 a transmission line network having at least three input/output terminals;   at least three transmit/receive units, respectively coupled to the at least three input/output terminals; and   a control system configured to, depending on a desired direction of data flow over the transmission line network, i) dynamically place each of the transmit/receive units in a transmit mode or a receive mode, and ii) dynamically enable and disable an active termination of each transmit/receive unit.   
     
     
         15 . The apparatus of  claim 14 , further comprising a test system, the test system having a test channel in which the at least three transmit/receive units are incorporated, the at least three transmit/receive units defining a 1:2 fan-out of the test channel. 
     
     
         16 . The apparatus of  claim 15 , wherein the test system comprises a plurality of the test channels. 
     
     
         17 . Apparatus for transmitting and receiving data, comprising:
 a transmit/receive unit having
 i) an input/output terminal; 
 ii) an active receiver having a receiver input coupled to the input/output terminal; 
 ii) an active driver having a driver input coupled to a driver output; 
 iii) a termination resistor coupling the driver output to the input/output terminal; and 
 iv) a switching element configured to selectively couple the driver input to i) a DC voltage source, and alternately, ii) a signal source. 
   
     
     
         18 . The apparatus of  claim 17 , wherein the switching element comprises a multiplexer having first and second multiplexer inputs, a multiplexer output coupled to the driver input, and a select input; wherein the DC voltage source is coupled to the first multiplexer input and the signal source is coupled to the second multiplexer input. 
     
     
         19 . The apparatus of  claim 17 , further comprising an adjustable delay element coupled to a receiver output of the active receiver.