Data processing apparatus

Claim 1

IN A DATA PROCESSING SYSTEM EMPLOYING BINARY CODED GROUPS OF SIGNALS FOR REPRESENTING DATA AND WHEREIN A PARITY SIGNAL IS USED TO MAINTAIN A FIXED PARITY IN EACH GROUP, AND ADDER CIRCUIT HAVING INPUTS ARRANGED FOR INCREMENTING OR DECREMENTING A NUMBER DEFINED BY A GROUP OF SIGNALS RECEIVED AT SAID INPUTS IN ACCORDANCE WITH ONE OR MORE CONTROL SIGNALS, A PARITY MODIFIER CIRCUIT HAVING INPUTS FOR RECEIVING CERTAIN OF SAID GROUP OF NUMBER SIGNALS AND PROVIDING, WHEN NECESSARY, AN OUTPUT SIGNAL FOR MODIFYING SAID PARITY SIGNAL OF SAID RECEIVED NUMBER SIGNALS IN ACCORDANCE WITH THE AMOUNT BY WHICH SAID NUMBER SIGNALS ARE INCREMENTED OR DECREMENTED, MEANS FOR APPLYING SAID NUMBER SIGNAL GROUP AND SAID PARITY SIGNAL TO SAID ADDER CIRCUIT, MEANS FOR APPLYING SAID NUMBER SIGNALS AND SAID ONE OR MORE CONTROL SIGNALS TO SAID PARITY MODIFIER CIRCUIT, MEANS FOR APPLYING SAID PARITY MODIFIER OUTPUT SIGNAL TO SAID ADDER CIRCUIT, AND A PARITY CHECKING CIRCUIT HAVING INPUTS FOR RECEIVING OTHER SIGNALS REPRESENTING SAID INCREMENTED OR DECREMENTED NUMBER AND PROVIDING AN ERROR SIGNAL WHEN SAID RECEIVED OTHER SIGNALS HAVE INCORRECT PARITY.