Patent Publication Number: US-2004055778-A1

Title: Apparatus and method for a flexible cable coupling an emulator unit with a target processor

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates generally to digital signal processing systems and, more particularly, to providing an interface between a target processor an emulator unit. The cable coupling the emulator unit and the target processor must carry a multiplicity of signals.  
       [0003] 2. Background of the Invention  
       [0004] The chips having at least one integrated circuit processing unit and/or at least one digital signal processor fabricated thereon have gotten increasingly complex. A chip can have literally dozens of individual processors included thereon. The testing of these chips along with the operation and validation of application-related software has become increasingly important and increasingly complex. To further complicate the problem, the test and debug procedure should generally be performed as rapidly as possible. All of these factors have converged to place stringent requirements of the interface between the processor(s) under test and the testing apparatus.  
       [0005] Currently, the interface to and testing of a chip involves apparatus dedicated to that purpose. Referring to FIG. 1, a block diagram of a test configuration is shown. The test configuration in the target processor (or chip)  12 , an emulation unit  11  and a host processing unit  10 . The host processing unit  10  and the emulation unit  11  are coupled by connector cable  14  and the emulation unit  11  and the target processor  12  are coupled by connector cable  15 . As will be clear, the host processing unit  10  and the target processor  12  can be combined in a single component. The target processor  12  has conductors coupled to numerous paths in the circuitry of the target processor. In this manner, the time dependence of the monitored signals provides information concerning the operation and performance of the circuit. The signals from the target processor  12  are applied to the emulation unit  11  over cable  15 . The emulation unit  11  acts as an interface between the signals generated by the target processor  12  and the data processing unit  10  where the signals are analyzed. For example, the connector cable  15  will typically have more conductors than the cable connector  14 . Consequently, one of the functions of emulation unit  11  is to store the test signals until the transfer to the data processing unit  10  can be effected.  
       [0006] While the connector cable  14  between the data processing unit  10  and the emulation unit  11  is typically of a size to couple to a standard connector of a data processing unit  10 , the connector cable  15  between the emulation unit and the target processor is frequently much larger. Referring to FIG. 2A and FIG. 2B, a typical ribbon connector cable  20  used to couple a target processor  12  and an emulation unit  11  is shown. The connector cable  20  has a connector  21 A and  21 B at each end. The connectors  21 A and  21 B couple to mating connectors on the target processor  12  and the emulation unit  11 . The cable portion  25  of the connector cable  20  has multiplicity of conductors  23  embedded in a flexible insulating matrix material  22 . The matrix material  22  can be plastic, rubber, or any other material that has suitable properties for constraining the conductors while insulating them from the other conductors. The matrix material  22 , if required, must be flexible to accommodate a wide variety of relative positions of the target processor  12  and the emulation unit  11 . Around the flexible matrix is a conducting material  24  to minimize the interaction with ambient electromagnetic fields and to prevent the signals carried by the conductors  23  from emitting radiation fields.  
       [0007] While the connector cable of the prior art has been used successfully, several disadvantages have been found. For example, the connector cable has proven not to be sufficiently flexible for use in field testing situations. Furthermore, the individual connector cable conductors generate cross-talk that can compromise the integrity of signal transmission and can limit the effective length and performance of the cable.  
       [0008] A need has therefore been felt for apparatus and an associated method having the feature of providing an improved cable for coupling an emulation unit and a target processor. It would be a further feature of the apparatus and associated method to provide a more flexible emulation unit/target processor connector cable. It would be a still further feature of the present invention to provide an emulation unit/target processor having a reduced cross-talk between the individual conductors. It would be yet a further feature of the present invention to provide improved skew relationships between the signals transmitted by the cable.  
       SUMMARY OF THE INVENTION  
       [0009] The aforementioned and other features are obtained, according to the present invention, by fabricating an emulation unit/target processor connector cable from a multiplicity of electrically shielded cables. The electrically shielded cable have center conductor surrounded by a suitable dielectric material. Enclosing the dielectric material and center conductor is a conducting tube. Surrounding the conducting tube is a dielectric matrix. The dielectric matrix can be processed in such a manner that the neighboring coaxial cables can be physically connected to form a cable connector. The center conductors are coupled to the pins of the connectors at either end of the connector cable.  
       [0010] Other features and advantages of the present invention will be more clearly understood upon reading of the following description and the accompanying drawings and the claims. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a block diagram of the test/interface configuration for testing, validation or application program of a target processing unit or chip according to the prior art.  
     [0012]FIG. 2A illustrates a connector cable used in coupling an emulation unit with a target processor according to the prior art, while FIG. 2B is a cross-sectional view of the connector cable shown in FIG. 2A.  
     [0013]FIG. 3A illustrates the connector cable used in coupling an emulation unit and a target processor according to the present invention. FIG. 3B is a cross-sectional view of the connector cable of FIG. 3A, and FIG. 3C is a perspective view of the shielded cable. 
    
    
     PREFERRED EMBODIMENT  
     [0014] 1. Detailed Description of the Figures  
     [0015]FIG. 1, FIG. 2A, and FIG. 2B have been described with respect to the prior art.  
     [0016] Referring to FIG. 3A, FIG. 3B, and FIG. 3C, the connector cable  30  for electrically coupling an emulation unit  11  and a target processor  12 , according to the present invention, is shown. The connector cable includes cable body  35  with connectors  31 A and  31 B at either end of the cable body  35 . FIG. 3 b,  a cross-sectional view of the cable body  35  illustrates that the connector cable body is fabricated from a multiplicity of small coaxial cables  36 . The coaxial cables  36 , shown in a perspective view in FIG. 3C, include a center conductor  361 , an insulating dielectric material  362  surrounding the center conductor  361 , a conducting tube  363  surrounding the dielectric material  362  and the center conductor  361 , and a second dielectric material  363  surrounding the conducting tube  363 . A surrounding cover  37  encloses the cable body. As will be clear to those skilled in the art, the conducting tube  363  is typically coupled to ground potential. However, the conducting tube  363  can be allowed to electrically “float” for certain applications.  
     [0017] The second dielectric material  361  is coupled to the dielectric material of adjoining coaxial cables  36  to form the connector cable body.  
     [0018] 2. Operation of the Preferred Embodiment  
     [0019] The individual coaxial cables are extremely flexible and employed in many normally unacceptable configurations. When mechanically coupled together, some of the flexibility is lost. However, even with the lost flexibility, the connector cable of the present invention is more flexible than the connector cable of the prior art. The use of coaxial cables prevents cross-talk between the individual conductors. The outer cover protects the individual coaxial cables from stress tending to pull the coaxial cable for the cable body.  
     [0020] The connecting cable of the present invention has been described as being detachably coupled to components by electrical connectors. The connecting cable can be electrically coupled to the associated components by any accepted techniques.  
     [0021] While the invention has been described with respect to the embodiments set forth above, the invention is not necessarily limited to these embodiments. Accordingly, other embodiments, variations, and improvements not described herein are not necessarily excluded from the scope of the invention, the scope of the invention being defined by the following claims.