This invention provides an iterative PCZZ data decoder that includes circuitry for utilizing all extrinsic information during iterative decoding by updating likelihood information for parity bits LPi, i=1, . . . , M during iterations. The extrinsic information for the parity bits is included in iterations by re-calculating soft values for parity bits LPi(k) for each iteration k. In one embodiment the parity bit soft values are re-calculated in a plurality of circuit blocks following Max-Log-APP (MLA) decoder blocks, based on soft values for data bits LDi(k). In another embodiment the parity bit soft values are re-calculated recursively within the plurality of MLA decoders. The decoder operates to control the convergence of the decoder by monitoring a soft value of one parity check symbol, e.g., L(k−1)[p(IM)], where p(IM) represents the last parity check bit in an I×M parity check array. A decoder iteration stopping rule may be implemented by testing a likelihood measure associated with a last parity check symbol in a parity check column. In one case the likelihood measure may be given by L(k−1)[p(IM]>threshold, and in another case the likelihood measure may be given by L(k−1)[p(I)]>threshold. The likelihood measure is given in general by: L(k−1)[p(I)]>threshold, L(k−1)[p(2I)]>threshold, . . . , L(k−1)[p(IM)]>threshold, where the value of the threshold is a function of data block size.