Many modern and emerging designs require having efficient dynamically reconfigurable and reprogrammable processors. However, when the implemented design needs an upgrade, newly added features have to be quickly supported and validated. This is clearly noticed in modern receivers of recent wireless communication standards that feature continuously different frame lengths and code rates for the channel decoder. This paper explores with an example the possibility of realizing a flexible channel decoder to implement and validate new/incremental algorithm changes with fast turnaround time in design. An application specific instruction-set processor (ASIP) is proposed as flexible core that can decode low-density parity-check (LDPC) codes with the various block sizes and code rates as specified in WiFi and WiMAX standards. Furthermore, the proposed architecture enables quick support of other Quasi-Cyclic LDPC (QC-LDPC) codes, e.g. DVB-S2, with simple incremental hardware changes at design time.