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Data port selection

  • US 4,920,511 A
  • Filed: 12/09/1987
  • Issued: 04/24/1990
  • Est. Priority Date: 12/12/1986
  • Status: Expired due to Fees
First Claim
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1. Apparatus for selecting one of a plurality of parallel data ports and for transferring data between the one port and a serial data path, the apparatus comprising:

  • (a) a first shift register having a serial data input coupled to the serial data path and having a parallel output;

    (b) at least one respective further shift register for coupling with a respective one of the parallel data ports and having a respective serial data terminal coupled to the serial data path and having a plurality of stages, the serial data terminal being one of an input and an output, according to whether the further shift register is for coupling with an output or an input parallel data port, respectively;

    (c) a plurality of respective means for coupling the stages of said at least one further shift register to the plurality of parallel data ports, there being one respective means for coupling for each of the plurality of parallel data ports and each of said respective means for coupling having a respective enable control input;

    (d) further means for coupling the parallel output of the first shift register to the enable control inputs of the respective means for coupling; and

    (e) means for enabling said further means for coupling to select and enable one of said respective means for coupling, that corresponds to the one port, according to contents of the first shift register.

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