JPH01184704A - Gain control system - Google Patents

Abstract

PURPOSE:To prevent a gain control amplifier from being disabled at its gain setting, to prevent a data output from being saturated and to prevent a tape mark from being undetected by amplifying the amplitude level of an output signal from an amplitude reference area in stages and comparing the output amplitude with a prescribed reference level. CONSTITUTION:A slice voltage obtained from a slice voltage generating circuit 6 is compared with a signal level outputted from a differentiating circuit 4 for a head output obtained from a magnetic head 1 and a gain control circuit is driven through a gain setting circuit 8 until both the values coincide with each other to automatically execute gradational gain control. The number of steps of the gradational gain is counted up by a prescribed number by a counter 7, and when a slice level can not be obtained, a slice voltage generating circuit 6 is driven to drop the slice level. If a VAL/SNS signal is outputted at the time of dropping the slice level, the count number is reduced down to the previously determined value to allow a program go to the succeeding data block. Consequently, problems such as the undetection of a tape mark due to the excessive amplification of noise can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gain control method, and particularly to a gain control method for a magnetic tape device.

[Conventional technology]

In the group code number recording (hereinafter referred to as OCR) mode in a conventional magnetic tape device, the readout circuit operates within the amplitude reference area (hereinafter referred to as ARA) provided immediately after the start point BOT of the magnetic tape. Increase the system gain in steps.

The output of the gain control amplifier does not reach the specified level.

In some cases, it became impossible to set the gain. Related to this type of technology is Japanese Patent Application Laid-Open No. 57-33416 [The problem to be solved by the invention +] In the above-mentioned conventional technology, when the gain is set near the highest step, the primary data block There were problems such as output saturation and tape marks not being detected due to excessive noise amplification.

An object of the present invention is to provide a gain control method that can avoid the inability to set the gain of a gain control amplifier due to defects in the ARA section of a magnetic tape, and to avoid saturation of data output and non-detection of tape marks. If the VAL/'SNS signal is output when the slice level is lowered, the count number is lowered to a predetermined value and the process proceeds to the next data block.

If the VAL-8NS signal is not output when the slice level is lowered, 5AGC-CHK is set and writing is prohibited, eliminating problems such as data output saturation and undetected tape marks due to excessive noise amplification. , achieved.

[Effect]

The head output read by the magnetic head is amplified via a preamplifier and a gain control circuit. In the level comparison circuit,
The signal level of the differentiating circuit of the slice voltage from the slice voltage generation circuit and the head output obtained from the magnetic head is compared, and the signal level is automatically applied to the gain control circuit via the gain setting circuit until these values match. Tonal gain adjustments are made.

The number of steps of this gradation gain is counted up to a predetermined count number by a counter, and if the slice level is not obtained, the slice voltage generation circuit is operated to lower the slice level. VAL-8N when lowering the slice level
When the S signal is output, the count number is lowered to a predetermined value and the process proceeds to the next data block. If the VAL-8NS signal is not output when the slice level is lowered, by setting 5AGC-CHK and inhibiting writing, problems such as data saturation and non-detection of tape marks due to excessive noise amplification will not occur.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a signal from a magnetic head 1 is input to a preamplifier 2. In FIG. VRI is a variable resistor that is used to correct variations in the read voltage of the head circuit system in PE mode. The signals successively output from the magnetic head 1 are input to a gain control circuit 3 via a preamplifier 2 for further amplification. This gain control circuit 3 is configured so that its gain is adjusted based on a digital signal transmitted from a gain setting circuit 8. The signal amplified by the gain control circuit 3 is input to the differentiation circuit 4. This differentiating circuit 4 is an amplifier that detects the signal peak of the gain control circuit 3. The signal differentiated by the differentiating circuit 4 is then connected to a level comparing circuit 5.

This level comparison circuit 5 determines whether or not the analog waveform amplitude differentiated by the differentiator 4 is a specified value. has been done. The gain setting circuit 8 adjusts the gain of the gain control circuit 3 and includes a gain up signal generating section. This gain up signal generating section has a 4-bit control signal in order to have steps of 1.alpha. to 15.alpha. The gain up signal generator steps 1α to 15α are configured to generate digital signals based on the control signal transmitted from the level comparison circuit 5, thereby controlling the gain of the gain control circuit 3. 7 counts up the gain up signal with a counter, and for example, V until the count number 101C is reached.
If the AL-8NS signal is not detected, it acts on the slice voltage generation circuit to lower the slice level. 9 is an and gate.

The output signal VAL-8NS Shinshu from the gain setting circuit 7 and the write control signal WRT-P are ANDed.

5AGC fist CHK signal is output.

FIG. 2 shows the step gain curve, the timing of the VAL-8NS signal and the 5AGC-CHK signal.

〔Effect of the invention〕

According to the present invention, even if there is a defect in the ARA area of the magnetic tape, it is possible to write data within a range that corresponds to the performance of the magnetic tape, thereby improving compatibility with other magnetic tape devices. This has the advantage of being able to write data on the tape at a writing quality that maintains the quality. Furthermore, since it is possible to prevent the gain set value from increasing during reading, it is possible to avoid saturation of data output and non-detection of tape marks.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus implementing a gain control method according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the structure shown in FIG. 1. 1...Magnetic head, 2...Preamplifier. 3... Gain control circuit, 4... Differential circuit. 5...Level comparison circuit. 6...Slice voltage generation circuit. 7...Counter, 8...Gain setting circuit. 9...and gate. Fig. f Fig. 2, -y- 1-''

Claims (1)

[Claims] 1. In a gain control method for a magnetic tape having an amplitude reference area and a data block, the amplitude level of an output signal in the amplitude reference area is amplified in a stepwise manner, and this output amplitude is compared with a predetermined reference level to obtain a predetermined value. If the amplitude level does not reach the reference level within the time
A gain control method characterized in that the reference level is lowered within a predetermined range, and when the amplitude level exceeds the reference level, the gain is set to a predetermined setting value and write inhibition is canceled.