Combined LDPC (Low Density Parity Check) encoder and syndrome checker. A novel approach is presented by which the encoding processing and at least a portion of the decoding processing of an LDPC coded signal can be performed using a shared circuitry. The LDPC encoding processing and syndrome calculation operations (in accordance with the LDPC decoding processing) can be performed using a common circuitry having a portion of which whose connectivity is only slightly modified depending on whether encoding or decoding is being performed. To effectuate this selection (between encoding and decoding), any of a variety of means can be employed including the use of multiplexers that are operable to select a first connectivity (for encoding) and a second connectivity (for decoding). This can result in a hardware savings of space, cost, and complexity since a shared circuitry can perform both encoding and at least part of the decoding processing.