| 摘要 |
PURPOSE:To enable accurate detection of speed even for an apparatus vary frequency in the starting and stopping of a pulse generator, by latching the contents of a counter according to a scan pulse or a synchronization demand signal. CONSTITUTION:An N' latch buffer 9 is added between a counter 6 and an O latch buffer 8 to latch the contents of the counter 6 according to an input of a scan pulse P1 or a synchronization demand signal P2. The pulse P1 is outputted from a scan pulse generator 2 at each fixed cycle set with a scan time setter 3, but when the signal P1 is inputted through an OR circuit OR1, the pulse P1 is generated in a specified time after the inputting thereof to synchronize a scanning. An N latch buffer 7 latches counting contents at each pulse P1 while the buffer 9 latches the contents of the counter 6 at a time of the pulse P1 or the signal P2 and moreover, a buffer 8 latches the contents of the buffer 9 at each pulse P1. This enables accurate detection of revolutions of a pulse generator 4 even in a circuit having a scan synchronization.
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