To provide a load drive control circuit which can retard malfunction of a load even if a fault occurs in the diagnostic wiring system.
A three-bridge motor drive circuit 8 is provided with a system control circuit 9 performing general control of the motor drive circuit 8, and a drive control circuit 10 serving as a driver and driving two motors M1 and M2. A diagnostic line S3 consisting of a plurality of signal lines is provided between the system control circuit 9 and the drive control circuit 10. In the sleep mode, the drive control circuit 10 delivers a diagnostic confirmation notice Sk1 where all diagnostic wiring outputs are in L state to the system control circuit 9. In the stand-by mode, the drive control circuit 10 delivers a diagnostic confirmation notice Sk2 where all diagnostic wiring outputs are in H state to the system control circuit 9, thus making the system control circuit 9 confirm the presence of failure in a diagnostic line L3.
URUNO TOSHIKI
NAGAO TAKASHI
CHIKAZAWA SATOSHI
Makoto Onda
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