JPS6446265A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent a medium defect from being erroneously detected as an address mark by storing a medium defect position beforehand, and prohibiting the detection of the address mark when the instruction to detect the address mark is received and while the present position of a head is coincident with the stored medium defect position. CONSTITUTION:When the medium detect position stored by a defect position storing circuit 1 is coincident with the present position of the head indicated by a head address register 2, a cylinder register 3 and a rotation position detecting circuit 4, a comparing circuit 5 outputs a prohibiting signal 6. An address mark detection instructing signal 7 is received, a flip flop circuit 10 to arrive at a part, where data are omitted, is set, and when the prohibiting signal 6 is active, namely, when the signal 6 is at the medium defect position stored by the present position of the head, a counter-up signal 12 or a counter- down signal 13 in a counter circuit 11 is not outputted. Thus, when the present position of the head is the stored medium defect position, the detection of the address mark is prohibited.