Abstract A digital capstan servo circuit controls the rotation of a capstan motor used for sending a recording medium of a recording apparatus having a recording circuit for recording a plurality of pilot signals instead of CTL signals used for a tracking servo of the capstan motor in a reproducing mode. The pilot signals have different frequencies respectively and are recorded under being mixed with a video signal on video tracks. In the recording mode, rotation speed information obtained from a counter (3) of which a counting value is latched by a latch pulse produced by a generator (27) from the FG signals which are generated synchronously with the rotation of the capstan motor and rotation phase information obtained from the counter (3) of which a counting value is latched by a latch pulse produced by a generator (28) from the output of an oscillator, an output signal of the oscillator having the same frequency as that of but a different phase from as that of the FG signals, are mixed to be a control signal of the capstan motor.
A digital servo circuit used for controlling a rotation of a motor comprising: (a) means for generating FG pulses in response to the rotation of said motor; (b) means for generating clock pulses (CK); (c) means (21) for generating a window pulse from said FG pulses; (d) means (3, 22) for counting said clock pulses during a period in which said window pulses is generated, said counter means being self reset during said period; (e) means (27) for generating a first latch pulse from said FG pulses used for latching a first counting value of said counting means at a first timing position for obtaining a rotation speed information; (f) means (28) for generating a second latch pulse used for latching a second counting value of said counting means at a second timing position for obtaining a rotation phase information; and (g) means (25A,25B,20) for producing a control signal by . mixing said first and second counting values.
Claim 2
Dependent Claim
158 words
A digital servo circuit used for controlling a rotation of a motor comprising: (a) means for generating FG pulses in response to the rotation of said motor; (b) means for generating clock pulses (CK); (c) means (21) for generating a window pulse from said FG pulses; (d) means (3, 22) for counting said clock pulses during a period in which said window pulses is generated, said counter means being self reset during said period; (e) means (27) for generating a first latch pulse from said FG pulses used for latching a first counting value of said counting means at a first timing position for obtaining a rotation speed information; (f) means (28) for generating a second latch pulse used for latching a second counting value of said counting means at a second timing position for obtaining a rotation phase information; and (g) means (25A,25B,20) for producing a control signal by . mixing said first and second counting values.
Claim 3
Dependent Claim
34 words
A digital servo circuit according to claim 1, further comprising a detecting circuit for detecting a lock condition of said counting means and for obtaining said rotation speed information and rotation phase information independently.
Claim 4
Dependent Claim
36 words
A digital servo circuit according to claim 2, in which said control signal producing means has a pair of D/A converters (25A,25B) and a mixer (20) for mixing a signal from said pair of D/A converters.
Claim 5
Dependent Claim
37 words
A digital servo circuit according to claim 3, in which frequencies of said first and second latch pulses are equal to each other but phases of said first and second latch pulses are different from each other.
Claim 6
Dependent Claim
87 words
A digital servo circuit, according to claims 1,2,3 or 4, further comprising means for setting said second counting value to a mean value when said motor is in an unlock condition. 6. A digital servo circuit according to any one of the preceding claims when used in the control of a motor of a magnetic recording apparatus having a recording circuit for recording a plurality of pilot signals mixed with a video signal on video tracks intead of control (CTL) pulses used for a tracking servo circuit.
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