DIAGNOSING SYSTEM FOR ERROR CORRECTING CIRCUIT

PURPOSE:To execute a correcting action in various cases and to execute the checking concerning the logic of a correcting circuit as a whole at an error correcting circuit by generating a pattern which cannot be reversely converted and a pattern which can be reversely converted and is erroneous as the data after conversion. CONSTITUTION:At the time of a self-diagnosing action, further, in 8 9 converting circuit 6 for diagnosis, the function to generate a pattern which can be reversely converted and comes to be erroneous as the data after conversion is added by giving an instruction with a control line 17 for diagnosis. If the data are read by a reading circuit 2, the reverse conversion can be executed and an external pointer can be generated by a 9 8 converting device 11. On the other hand, by processing the data after reverse conversion with a syndrome processing device 14, it is found that the error exists. In an internal pointer generating circuit 15 from the processed syndrome value, the information at which track the error exists is transferred to an error pattern generating device 16 by an internal pointer information transferring line 19. Thus, the internal pointer generating device 15 is checked.