JPS62180570A - Cylinder pulse generating circuit - Google Patents

Abstract

PURPOSE:To generate accurate cylinder pulse resistant to noise by outputting cylinder pulse by the output of a timer and preventing the resetting of the timer by noise while timer output exists. CONSTITUTION:In a magnetic disk device having a servo track system, a speed signal 6 that indicates the moving speed of a servo head is inputted to an A/D converter 1, and a ROM 2 outputs a timer value corresponding to a digital speed signal. A timer circuit 3 makes a timer output 7 an H level for a time corresponding to the input timer value from the leading of a trigger signal 9, and a one shot circuit 4 output cylinder pulse 10 at the leading of the timer output 7. A zero crossing detecting circuit 11 generates a pulse 12 at every time when a position signal 8 indicating the position of the servo head passes 0V, and an OR gate 5 prohibits the inputting to the timer circuit 3 while the output of the timer circuit exists. Thus, no influence is caused even when the position signal 8 passes 0V due to noise, etc., even when zero cross pulse 12 is inputted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic disk device having a servo track system, and more specifically, to a cylinder pulse generation circuit in the device.

(Prior Art) The servo track method detects when a servo head crosses a servo pattern and generates a cylinder pulse.

In other words, when the servo head crosses the servo pattern, the position signals +vr, θ, -Vr are detected, which are the maximum positive polarity at the even numbered servo pattern, θ at the middle of the servo pattern, and the maximum negative polarity at the odd numbered servo bar. By doing so, a pulse signal is generated.

FIG. 2 shows the relationship among this servo pattern, position signal, and cylinder pulse.

(Problems that the invention attempts to solve 11!4) However, since the conventional cylinder pulse generation circuit generates cylinder pulses only by detecting the level of the position signal, as shown in Fig. (If noise enters the blade of No. H, there is a drawback that if the noise component exceeds the ejection level, many cylinder pulses will be generated.

An object of the present invention is to provide a cylinder pulse generation circuit that is not affected by external noise.

(Means for Solving the Problems) To achieve the above object, a cylinder pulse generation circuit according to the present invention is provided in a cylinder pulse generation circuit in a magnetic disk drive having a servo track system. The speed signals indicating 1kyI speed are A and D.
A/D variable weapon to be converted, and R, OM in which a value having an inverse proportional relationship to the A/D converter output is stored, and a value corresponding to the A/D converter output is read out.
, a zero-crossing detection circuit for detecting the zero-crossing point of the position signal, and a timer that starts its operation according to the output pulse of the zero-crossing detection circuit and generates an output during the time of the value read from the R and OM. A pulse circuit that generates a cylinder pulse based on the output of the timer circuit, and a circuit that prohibits input to the timer circuit while the timer circuit is in operation.

(Example) Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a cylinder pulse generation circuit according to the present invention.

A/D converter 1 digitizes analog speed signal 6. ROM2 outputs a timer value corresponding to the digitized speed signal.

The timer circuit 3 inputs the timer value output from the ROM 2 at the rise of the trigger signal 9, and sets the timer output cuff corresponding to the input timer value to the H level from the rise of the trigger signal 9. The one-shot circuit 4 outputs a cylinder pulse 10 at the rising edge of the timer output cuff. (, I B gate 5 inputs the input t to the timer circuit 3 while there is an output from the timer circuit 3.
l-m stop.

The zero cross detection circuit 11 generates a pulse every time the position signal 8 passes through OV.

Speed signal 6 is a signal indicating the moving speed of the servo head,
The position signal 8 is a signal indicating the position 21 of the servo head.

FIG. 4 shows the circuit output of each part in the circuit of the present invention. Since the speed signal and the period of the cylinder pulse are inversely proportional to each other as shown in FIG. 4, the entire period of the cylinder pulse can be estimated by knowing the speed signal.

Speed signal 6'i is A/D converted and digitized, and the digitized speed signal is input to ROFJ2.

Since the cycle of the cylinder pulse can be estimated from the speed signal, H and OM are set so that the timer output 9 of the timer 3 is set to a value that is output for a slightly shorter time than the cycle of the cylinder pulse.

Therefore, the first shift of the output of H, (JM2 becomes smaller when the speed signal is large, and becomes larger when the speed signal is small.

FIG. 5 is an explanatory diagram of the operation when noise enters the position signal.

When the position signal 8 passes through OV, a zero cross is detected by the detection circuit 11, and a zero cross pulse 12 is output. When the output of the timer circuit 3 is at L level, the trigger signal 9 is at H level. Timer circuit 3
starts the operation by reading the output value of R, 0M3 at the time when the trigger signal 9 becomes H. During operation, the timer circuit 3 sets the timer output cuff to H level, and the one-shot circuit 4 operates according to the timer output cuff, and the cylinder pulse 10 is output.

Since the timer output cuff is at H level for the time corresponding to the output of ROM 2 at the time when trigger signal 9 is input, the trigger (H signal 9 is at H level until a little before the time when zero cross pulse 12 is input next) It becomes.

Therefore, even if the null position signal passes through Ov due to noise or the like during that time and the zero-cross pulse is input, it will not be affected.

(Effects of the Invention) As explained above in detail, the present invention changes the timer time of the timer circuit according to the speed signal, outputs a cylinder pulse according to the timer output, and uses the position signal as long as the timer output is present. By controlling the timer so that superimposed noise does not reset the timer, it is possible to generate accurate cylinder pulses that are resistant to noise.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the cylinder pulse generation circuit according to the present invention, Fig. 2 is a diagram showing the positional relationship of the servo butter 7, position signal, and cylinder pulse, and Fig. 3 is a diagram showing the positional relationship between the servo butter 7, the position signal, and the cylinder pulse. FIG. 4 is a waveform diagram showing the cylinder pulse in the case of FIG. 1 is a waveform diagram of a zero cross pulse, a timer output, and a cylinder pulse when noise is added to the position signal in this embodiment. 1...A/D conversion 2...ROM3...
Timer circuit 4...One-shot circuit 5...OR
Gate 6...Speed signal 7...Timer output 8...Position signal 9...Trigger signal 1
θ...Cylinder pulse 11...Zero cross detection circuit 12...Zero cross pulse

Claims (1)

[Claims] A cylinder pulse generation circuit in a magnetic disk drive having a servo track system includes an A/D converter that A/D converts a speed signal indicating the moving speed of the servo head, and a value having an inverse proportional relationship to the output of the A/D converter. A ROM is stored and a value corresponding to the output of the A/D converter is read out, a zero cross detection circuit detects a zero crossing point of a position signal indicating the position of the servo head, and an output pulse of the zero cross detection circuit is used. A timer circuit that starts operation and generates an output during the time of the value read from the ROM, a pulse circuit that generates a cylinder pulse based on the output of the timer circuit, and a pulse circuit that generates a cylinder pulse based on the output of the timer circuit; 1. A cylinder pulse generation circuit comprising: a circuit for inhibiting input; and a circuit for inhibiting input.