Integrated memory having redundant units of memory cells, and test method for the redundant units

A method for testing redundant units of an integrated memory, the method which comprises:

• providing an integrated memory having memory cell configurations with normal units and redundant units, the normal units being addressable by addresses having a width of m bits, the redundant units configured for replacing respective ones of the normal units with regard to the addresses;
• providing, for each of the redundant units, respective m programmable elements for storing an address of one of the normal units to be replaced;
• providing, for each of the redundant units, respective n<m first comparison units and m-n second comparison units having respective outputs for comparing the address stored by the programmable elements with an address fed to the integrated memory;
• providing, for each of the redundant units, a respective code converting unit having n inputs and having n outputs,
• supplying the code converting unit with n bits of the address fed to the integrated memory;
• subjecting, with the code converting unit, the n bits to a respective type of code conversion and forming n output bits, the respective type of code conversion being different for each of the redundant units;
• providing, for each of the redundant units, a respective logic unit having n first inputs and having m-n second inputs for performing an AND function;
• generating, with the logic unit, an activation signal for a respective one of the redundant units, the second inputs of the logic unit being connected to the outputs of the second comparison units;
• providing, for each of the redundant units, a respective multiplexer having n first multiplexer inputs, n second multiplexer inputs and n multiplexer outputs, the n multiplexer outputs being connected to the n first inputs of the logic unit;
• and
• selectively bringing the multiplexer into a first switching state for connecting the outputs of the first comparison units to the first inputs of the logic unit, and, while the programmable elements are in an unprogrammed state, bringing the multiplexer into a second switching state for connecting the outputs of the code converting unit to the first inputs of the logic unit.