Apparatus and method for memory read-refresh, scrubbing and variable-rate refresh

A memory controller and method that provide a read-refresh (also called "distributed-refresh") mode of operation, in which every row of memory is read within the refresh-rate requirements of the memory parts, with data from different columns within the rows being read on subsequent read-refresh cycles until all rows for each and every column address have been read, scrubbing errors if found, thus providing a scrubbing function that is integrated into the read-refresh operation, rather than being an independent operation. For scrubbing, an atomic read-correct-write operation is scheduled. A variable-priority, variable-timing refresh interval is described. An integrated card self-tester and/or card reciprocal-tester is described. A memory bit-swapping-within-address-range circuit, and a method and apparatus for bit swapping on the fly and testing are described.