Techniques for the reading and writing of data in multi-state non-volatile memories are described. Data is written into the memory in a binary format, read into the data registers on the memory, and “folded” within the registers, and then written back into the memory in a multi-state format. In the folding operation, binary data from a single word line is folded into a multi-state format and, when rewritten in multi-state form, is written into a only a portion of another word line. A corresponding reading technique, where the data is “unfolded” is also described. The techniques further allow for the data to be encoded with an error correction code (ECC) on the controller that takes into account its eventual multi-state storage prior to transferring the data to the memory to be written in binary form. A register structure allowing such a “folding” operation is also presented. One set of embodiments include a local internal data bus that allows data to between the registers of different read/write stacks, where the internal bus can used in the internal data folding process.