JPH0132207Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an index pulse signal processing circuit for a disk device.

(Prior Art) In a disk device, for example, a magnetic disk device, data is written and read based on an index pulse that is generated once per rotation of the disk. Therefore, it is necessary to accurately determine the position of the index pulse, but when the index pulse is generated by a disk drive motor, that is, a spindle motor, it is necessary to accurately determine the position of the index pulse. An index pulse is generated slightly before the reference index pulse position in a manner similar to detection, and this index pulse is delayed by an index pulse signal processing circuit to adjust its position to the reference index pulse position. There is.

Such an index pulse signal processing circuit is composed of two mono-multivibrators M1 and M2, as shown in FIG. As shown in Fig. 4, mono multivibrator M1 is triggered at the leading edge of the index pulse input and outputs a pulse with pulse width T, and mono multivibrator M2 is triggered at the trailing edge of this pulse and outputs a pulse with pulse width T.
Outputs td index pulse. The position of this index pulse is the mono multivibrator M.
By adjusting the values of variable resistor VR1 and capacitor C1 of 1 and changing T, the position can be adjusted to the normal position.
td is determined by adjusting the values of variable resistor VR2 and capacitor C2.

(Problem that the invention attempts to solve) In the above index pulse signal processing circuit, the IC
(Integrated circuit) In this case, the portion excluding variable resistors VR1, VR2 and capacitors C1, C2 is constructed with an IC, and variable resistors VR1, VR2 and capacitors C1, C2 are externally attached to this. Therefore, an IC requires at least six pins P1 to P6, and if the number of IC pins is limited to less than six, it cannot be made into an IC.

(Means for Solving the Problems) The present invention provides an index pulse signal processing circuit for a disk device that writes or reads data based on the index pulse. A variable time constant circuit for smoothing, a first comparison circuit and a second comparison circuit to which the output of the variable time constant circuit is input, and a second comparison circuit whose operation is controlled by the output of the second comparison circuit. and switching means for setting the reference voltage of the circuit to a value above or below the reference voltage of the first comparison circuit.

(Function) One edge of the index pulse input is smoothed by the variable time constant circuit, and
The output of the second comparison circuit controls the operation of the switching means to set the reference voltage of the second comparison circuit to a value above or below the reference voltage of the first comparison circuit. The outputs of the comparison circuit and the second comparison circuit form an index pulse.

(Embodiment) FIG. 1 shows an embodiment of the present invention, and FIG. 2 is a timing chart thereof.

Comparators CP1, CP2, transistor Tr,
Inverters N1 to N3 and resistors R1 to R8 are composed of an IC (integrated circuit), and this IC has two pins P.
7, P8 are provided. The variable resistor VR3 and the capacitor C3 constitute a variable time constant circuit, and the above
Externally attached to the IC. Comparator CPI and resistance R
1 to R3 constitute a first comparison circuit that compares the input voltage with the reference voltage V _TH1 , and the power supply voltage V _CC is connected to the resistor R1.
The voltage is divided by ~R3 and applied to the comparator CP1 as a reference voltage _VTH1 . Comparator CP2 and resistors R4 to R6 constitute a second comparison circuit that compares the input voltage with reference voltage V _TH2 , and the power supply voltage V _CC is divided by resistors R4 to R6 to
is given as the reference voltage V _TH2 . transistor
The Tr is used as a switching means, and depending on the output of the comparator CP2, a part of the resistor R5 and the resistor R6 are short-circuited or not short-circuited to set the reference voltage V _TH2.
Switch to a value lower or higher than the reference voltage V _TH1 .

An index pulse is input to pin P7 from a sensor that detects a detection section provided on the rotor of a disk drive motor in a magnetic disk device. When a low-level index pulse is input to pin P7, both ends of capacitor C3 are shortened and the capacitor C3 is instantly discharged, and when no index pulse is input to pin P7, it becomes an open circuit and the supply voltage V _CC is charged through variable resistor VR3. During the process in which capacitor C3 is discharged by the index pulse input and pin P7 becomes low level, the output of comparator CP1 is first inverted and becomes high level, and after a slight delay, the output of comparator CP2 changes from high level to low level. to be reversed.

Before the index pulse is input to pin P7, comparator CP2 outputs a high level because the charging voltage of capacitor C3 input to the non-inverting input terminal is higher than the reference voltage V _TH2 input to the inverting input terminal. Then, the transistor Tr is turned on and the reference voltage V _TH2 is maintained at a predetermined level lower than the reference voltage V _TH1 . Comparator CP1 is pin P
7, the charging voltage of capacitor C3 input to the inverting input terminal is the reference voltage V _TH1 input to the non-inverting input terminal.
Because it is higher, the output is at a lower level.

When the capacitor C3 is discharged by the index pulse input and the output of the comparator CP2 becomes low level, the transistor Tr is turned off and the reference voltage
VV _TH2 becomes higher level than reference voltage V _TH1 . When the index pulse input disappears in this state, the capacitor C3 is charged by the power supply voltage V _CC through the variable resistor VR3 with a time constant of C3 and VR3, and this charging voltage is applied to the comparators CP1 and CP2.
is input. Therefore, first the comparator CP
The output of comparator CP2 is inverted and becomes a low level, and then the output of comparator CP2 is inverted and becomes a high level.
The outputs of the comparators CP1 and CP2 are each inverted by inverters N1 and N2, a wired OR is taken, and the outputs are inverted by an inverter N3 and output from pin P8 as an index pulse. This index pulse is generated during the period when the outputs of inverters N1 and N2 are both at a low level, that is, during the period from when the input of the index pulse disappears and the output of comparator CP1 is inverted until the output of comparator CP2 is inverted. , the position is determined by the charging curve of the capacitor C3, that is, the charging time constants C3 and VR3. Therefore, the position of the index pulse can be adjusted to the normal position by adjusting the variable resistor VR3. When the capacitor C3 is discharged by inputting the index pulse, the transistor
Since the reference voltage V _TH2 is switched to a level lower than the reference voltage V _TH1 by the Tr, the comparator CP
The outputs of 1 and CP2 never reach a high level, and no index pulse is output.

Although the transistor Tr is used as the switching means for switching the reference voltage V _TH2 , an analog switch may also be used.

(Effects of the invention) As described above, according to the invention, one edge of the index pulse input is blunted by the variable time constant circuit and inputted to the first comparison circuit and the second comparison circuit, while the first edge Switching means is provided for setting the reference voltage of the second comparison circuit to a value below the reference voltage of the comparison circuit, and the operation of the switching means is controlled by the output of the second comparison circuit. Since the index pulse is formed by the output of the second comparator circuit, the number of pins can be reduced.
It becomes possible to convert it into an IC.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
This figure is a timing chart of the same embodiment, FIG. 3 is a circuit diagram showing an index pulse signal processing circuit of a conventional disk device, and FIG. 4 is a timing chart of the same index pulse signal processing circuit. VR3...variable resistor, C3...capacitor, CP
1, CP2... Capacitor, N1-N3... Inverter, R1-R8... Resistor.

Claims (1)

[Scope of utility model registration request] In an index pulse signal processing circuit of a disk device that writes or reads data based on the index pulse,
One edge of the index pulse input is rounded by a variable time constant circuit and inputted to the first comparison circuit and the second comparison circuit, while a second A switching means is provided for setting a reference voltage of the comparison circuit, the operation of the switching means is controlled by the output of the second comparison circuit, and an index pulse is generated by the output of the first comparison circuit and the second comparison circuit. 1. An index pulse signal processing circuit for a disk device, characterized in that the index pulse signal processing circuit is configured to form an index pulse signal.