| 摘要 |
PURPOSE:To detect a fault and to secure the reliability of written data, and to prevent data on a recording medium from being destroyed, by inputting a preset testing pattern to a writing correcting circuit when the circuit is not in operation, and comparing its output with a test pattern. CONSTITUTION:Respective bits of data 1, 2, 3, and 4 in an ROM28 are set to flip-flops 1, 2, 3, and 4. When a counter 29 goes up to 4, count bits 7 and 8 are 0 and 0, so a decoder 26 outputs 1 and the output of a flip-flop 25 is also 1. At this time, EOR circuits 19-22 compare data 1, 2, 3, and 4 read out of the ROM28 and when data are coincident, its output is 0. When not, the output is 1 and sent to an AND circuit 24 through an OR circuit 23. Therefore, when a CLK3 is 1, the AND circuit 24 outputs 1 to report dissidence of a testing pattern. |
