JPS6136281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a write control method for a magnetic video disk device.

Since conventional magnetic video disk devices are intended for recording moving images, no countermeasures have been taken against instantaneous synchronization disturbances at the start of writing.
Therefore, when recording a still surface, writing is performed even during a period when the synchronization is disturbed, and when writing one frame, there are drawbacks such as image disturbance and moiré.

In view of the above-mentioned drawbacks of the prior art, the present invention provides a method for preventing writing during a period when the synchronization at the start of writing is disrupted.

The present invention monitors the rotational synchronization phase of the disk drive motor, and determines the timing of head switching based on the monitoring signal, a field signal for identifying even/odd fields, and a write command signal, thereby eliminating synchronization disturbance and achieving a stable state. This feature is characterized in that writing starts after recovery. The present invention will be described in detail below with reference to the accompanying drawings.

The attached figure is a block diagram showing one embodiment of the present invention, in which 1 is an input terminal for a write command signal;
The write command signal controls the write/reproduction changeover switch, and is also led to the head changeover control circuit 16. Reference numeral 2 denotes an input terminal for a video input signal, and the video input signal is led to a write amplifier 5 via a buffer amplifier 4, and then to a magnetic head 10 or 1 via a write regeneration switch 8 and a head switch 9.
I am guided by 1. The output of the write amplifier 5 is further led to a changeover switch 7, which selects either the output of the regenerative amplifier 6 or the output of the write amplifier 5. The output of the changeover switch 7 is the horizontal sync separation circuit 12 and the vertical sync separation circuit 22.
guided by. Output terminal 1 of horizontal synchronization separation circuit 12
3, a horizontal synchronization pulse is obtained. The output terminals of the vertical synchronization separation circuit 22 are output terminals 14 and 15. A vertical synchronization pulse is obtained at the output terminal 14, and a field signal for identifying whether the field is even or odd is obtained at the output terminal 15. The horizontal synchronization pulse and the vertical synchronization pulse are guided to a phase comparator 18, where the phases are compared with the output signal of a rotation detection device 21 that generates a pulse corresponding to the rotational speed of the motor. An output proportional to the phase difference between the synchronization signal and the rotation of the motor is obtained from the phase comparator 18, and the output is led to the motor drive circuit 19 and the phase synchronization monitoring circuit 17. The phase synchronization monitoring circuit 17 is the phase comparator 1
It monitors whether the output of No. 8 is within a specified value range, converts the result to a logical value of "0" or "1", and outputs the result. The output of the phase synchronization monitoring circuit 17 is led to the head switching control circuit 16, which logically processes the write command signal coming from the input terminal 1 and the field signal coming from the output terminal 15, to ensure synchronization. It is only when synchronization is reached again after the disturbance that the head changeover switch 9 is turned on.
Sends a switching signal to

As is clear from the above embodiments, according to the present invention, recording of still images is extremely stable because writing can be prevented during periods when synchronization is disrupted.

[Brief explanation of the drawing]

The accompanying drawing is a block diagram showing one embodiment of the present invention. 1... Interrupt signal input terminal, 2... Video signal input terminal, 3... Video signal output terminal, 4... Buffer amplifier, 5
...Write amplifier, 6...Regenerative amplifier, 7, 8, 9... Selector switch, 10, 11... Magnetic head, 12... Horizontal synchronization separation circuit, 13... Horizontal synchronization signal output terminal,
14... Vertical synchronization signal output terminal, 15... Field signal output terminal, 16... Head switching control circuit, 17
...Phase synchronization monitoring circuit, 18...Phase comparator, 19...
Motor drive circuit, 20... Disc drive motor, 2
1... Rotation detection device, 22... Vertical synchronization separation circuit.

Claims (1)

[Claims] 1. In a magnetic video disk control system, a rotation detection means that detects the rotation speed of a disk drive motor and generates a pulse according to the speed, and an output pulse of the rotation detection means and a horizontal synchronization pulse and a vertical synchronization pulse of the video. a phase comparison means for performing a phase comparison, a phase synchronization monitoring means for monitoring whether the output of the phase comparison means is within a specified value range, and outputting a phase synchronization monitoring signal in accordance with the output, and a write command. By logically processing the field signal that identifies whether the signal is even or odd and the phase synchronization monitoring signal, a switching signal is sent to the head selector switch and writing is performed only when synchronization is achieved again after the synchronization has been disrupted. 1. A write timing control method characterized by comprising a head switching control means for controlling a write timing.