Redundant element substitution apparatus

In a circuit having at least first and second data input lines and at least a first redundant data input line, apparatus for receiving data from said first and second data input lines and said redundant data input line and selectively outputting data, on at least first and second output lines, the apparatus comprising:

• at least first and second selection circuits, the first selection circuit having a multiplexor for receiving data from said first data input line and from said first redundant data input line, respectively, under control of a first control signal, and having a first output for outputting data to said first output line, said second circuit having a second multiplexor for receiving third and fourth inputs from said second data input line and said first data input line, respectively, and under control of a second control signal, outputting data to said second data input line;
• a first control line for conveying said first control signal from said second selection circuit to said first selection circuit, said first control signal being in a first or second state;
• a second control line for receiving a second control signal in said second selection circuit, said second control signal being in a first or second state;
• said first selection circuit having said first multiplexor configured to convey data from said first data input line to said first output line when said first control signal is in said first state and to convey data from said first redundant data input line to said first output line when said first control signal is in said second state;
• a fuse in said second selection circuit which can be in a blown or unblow state, and
• logic circuitry in said second selection circuit for
• conveying data from said second data input line to said second output line and for outputting a control signal on said first control line substantially identical to the control signal received on said second control line when said fuse is in said unblown state and for
• conveying data from said first data input line to said second output line and outputting a control signal on said first control line which is the inverse of said control signal received on said second control line, when said fuse is in said blown state.

In a circuit having at least first and second data input lines and at least a first redundant data input line, a method for receiving data from said first and second data input lines and said redundant data input line and selectively outputting data, on at least first and second output lines, the method comprising:

• providing at least first and second selection circuits, configurable in a first state or second state;
• configuring said selection circuits in said first state wherein data on said first data line is provided to said first output line and wherein data from said second data input line is provided to said second output line;
• and
• reconfiguring said selection circuits to a second configuration by blowing no more than a single fuse wherein data from said redundant data input line is provided to said first output line and data from said first data input line is provided to said second output line.

In a circuit having at least first and second data input lines and at least a first redundant data input line, apparatus for receiving data from said first and second data input lines, and said redundant data input line, and selectively outputting data, on at least first and second output lines, the apparatus comprising:

• at least a first selection circuit having a multiplexor for receiving two inputs and providing a single output under control of a control signal provided over a first control line;
• said first invertor having its input connected, by a blowable fuse, to a voltage source;
• said input of said invertor connected, by a transistor, to a ground voltage source;
• the gate of said transistor connected to the output of said invertor;
• a NOR gate with first and second inputs and a single output, said output connected to said first control line, said first NOR gate input connected to an input control line, said second NOR gate input connected to the output of a first invertor;
• the output of said NOR gate connected to the input of a second invertor;
• and
• the output of said second invertor provided to an output control signal line.