Addressable open connector test circuit

Abstract

An open circuit detection apparatus is provided for detecting whether a connection is closed between a local node and a remote node having a known impedance. A ping source is connected to the local node. The ping source has an output for transmitting an address unique to the remote node and an input for sensing the impedance of the remote node. A test circuit is connected to the remote node. The test circuit has an address decoder for receiving the address from the output. The address decoder has a unique address and asserts a control signal upon the address matching the unique address of said address decoder. An impedance-varying device is responsive to the control signal and effects a change in the impedance of the remote node. The change in the impedance of the remote node is sensed by the input of the ping source.

What is claimed is:  
     
         1 . An open circuit detection apparatus for detecting whether a connection is closed between a local node and a remote node having a known impedance, the apparatus comprising: 
 a ping source connected to the local node, said ping source further comprising 
 an output for transmitting an address unique to the remote node; and  
 an input for sensing the impedance of the remote node;  
   a test circuit connected to the remote node, said test circuit further comprising 
 an address decoder for receiving said address from said output, said address decoder having a unique address;  
 a control signal, said address decoder asserting said control signal upon said address matching said unique address of said address decoder; and  
 an impedance varying device being responsive to said control signal, said impedance varying device effecting a change in the impedance of the remote node; and  
   said change in the impedance of the remote node being sensed by said input of said ping source.    
     
     
         2 . The apparatus of  claim 1  wherein the address decoder is adapted to receive an n number of bits.  
     
     
         3 . The apparatus of  claim 2  wherein the impedance varying device is a transistor.  
     
     
         4 . A method for determining whether a connection is closed between a local node and a remote node, the method comprising; 
 transmitting a unique address from the local node, through the connection, to the remote node;    changing the impedance of the remote node in response to said unique address being received at the remote node;    sensing the impedance change of the remote node and determining therefrom that the connection is closed.    
     
     
         5 . The method of  claim 4  further comprising sensing an open impedance of the remote node and determining therefrom that the connection is open.  
     
     
         6 . The method of  claim 5  wherein said unique address is comprised of n-bits.  
     
     
         7 . The method of  claim 6  wherein said step of transmitting said unique address occurs when the connection is free from other communication.  
     
     
         8 . The method of  claim 7  wherein said step of determining the connection is closed further comprises a comparison between a voltage of the local node and a reference voltage.  
     
     
         9 . The method of  claim 8  wherein said step of determining the connection is open further comprises a comparison between said voltage of the local node and said reference voltage.  
     
     
         10 . In an open circuit detection apparatus for detecting whether a connection is closed between a local node and a remote node, the remote node having a known impedance, the apparatus having a ping source connected to the local node, the ping source having an output for transmitting an address unique to the remote node and an input for sensing the impedance of the remote node, a test circuit for effecting a change in the known impedance of the remote node, the test circuit comprising: 
 an address decoder for receiving the address from the output, said address controller having a unique address;    a control signal, said address decoder asserting said control signal upon the address matching said unique address of said address decoder; and    an impedance varying device being responsive to said control signal, said impedance varying device effecting a change in the impedance of the remote node, said change indicating to the input that the connection is closed.    
     
     
         11 . The apparatus of  claim 10  wherein said address decoder is adapted to receive an n number of bits.  
     
     
         12 . The apparatus of  claim 11  wherein said impedance varying device is a transistor.