JPS6128183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information reproducing device, and particularly to an information reproducing device such as a magnetic tape.

In magnetic tape devices, the gain of the amplifier is stepped in order to compensate for differences in tape output and head output so that the signal amplitude is almost constant before the signal read from the head is converted into digital information. is switching to For example tape speed 200IPS
(inch/second), and in a magnetic tape device with a recording density of 6250 BPI (bits/inch), near the beginning of the tape,
Record the signal at the highest recording density, play it back,
The gain of the amplifier is switched so that the signal amplitude remains constant. This amplifier is called a SAGC amplifier. FIG. 1 is a diagram showing the relationship between the head output and the output voltage of the SAGC amplifier. Here, the subscripts in the figure indicate the number of switching stages of the SAGC amplifier. For this gain adjustment, the recording signal is automatically recorded from the controller upon the first write command when the tape is used. This signal is called an abort signal.

However, if dust or the like adheres to the recording head, the gap between the head and the tape widens and the above-mentioned alabaster signal is no longer recorded, resulting in an extremely low reproduction output. In such a case, the gain of the SAGC amplifier is adjusted by the small-amplitude alabaster signal, so the amplifier has a high gain, and when a normal signal is reproduced, the amplifier saturates.
Waveform distortion occurs, causing errors. Also,
When dust adheres to the read head during reproduction, even if the alabaster signal is recorded normally, the reproduced signal becomes small, causing errors due to the waveform distortion described above.

An object of the present invention is to detect such an extreme increase in the gain of the SAGC amplifier and to prevent errors due to saturation of the amplifier.

The present invention will be explained below based on examples.

In the present invention, we focus on the fact that it is extremely rare for all tracks to experience a simultaneous decrease in output due to the above-mentioned dust adhesion, etc., and calculate the difference between the maximum and minimum number of SAGC amplifier stages for each track. If it exceeds a certain level, it is assumed that the alabaster signal was not recorded or reproduced normally, and the command is retried. In the device to which the present invention is applied, the SAGC amplifier exhibits the characteristics shown in Figure 1, and the gain is initially set from the lowest gain state (number of stages is 0) until the output reaches a certain amplitude.
A method is used in which the gain is increased by counting pulses that increase the gain (called setup pulses). Counting the difference between the maximum and minimum stages of gain setting of the SAGC amplifier can be easily realized, for example, with a circuit as shown in FIG.

FIG. 2 shows, by way of example, the embodiment of the invention in the case of a truck. Here, 10,2
0 and 30 indicate information recording circuits for each track. 11, 12, 13 are heads, 21, 22, 2
3 is a SAGC amplifier; 51, 52, and 53 are amplitude detection circuits; 61, 62, and 63 are setup pulse generation circuits; 41, 42, and 43 are 4-bit counters that count the setup pulses;
2 and 33 are D/A converters which D/A convert the output of this counter, and the gain of the SAGC amplifier is controlled by this output. First, in FIG. 1, the number of switching stages of the SAGC amplifier corresponds to the values of the counters 41, 42, and 43. The outputs of the SAGC amplifiers 41, 42, 43 pass through waveform processing circuits 71, 72, 73, pulse generation circuits 81, 82, 83, and then pass through lines 101, 102, 1
03 to the controller. Also
The output pulse of the SAGC amplifier is input to a 4-bit counter 3 via an OR circuit 1, where a value corresponding to the maximum number of stages is stored.

If this counter 3 overflows,
An overflow signal is sent to the controller via line 105.

Since the above configuration is well known, the details will be omitted.

The present invention is characterized by the provision of an AND circuit 2, an exclusive OR circuit 4, and a counter 5 to which a setup pulse is input. That is, when a setup pulse is input to the AND circuit 2 and the OR circuit 1, and its output is input to the exclusive OR circuit 4, the output is sent to the counters 41, 42, 43 in the information recording circuits 10, 20, 30. The number of pulses corresponding to the difference between the maximum and minimum stored values of is outputted, and this number is stored in the counter 5. If counter 5 is configured with a 3-bit counter, the difference between the maximum and minimum values of counters 41, 42, and 43 is 8.
If the amount exceeds the limit, an overflow signal is output. This overflow signal may be sent to the controller via line 104.

In the controller, if a signal is sent from the line 104, it is sufficient to instruct the controller to retry the command, that is, to rewrite the abort signal.

Note that FIG. 3 shows pulse signals related to the present invention, and (a), (b), and (c) are output examples of the setup pulse generation circuits 61, 62, and 63, respectively;
(d) and (e) show output examples of the OR circuit 1 and AND circuit 2, respectively, and (f) shows an output example of the exclusive OR circuit 4.

[Brief explanation of the drawing]

FIGS. 1 to 3 are diagrams illustrating embodiments of the present invention. 21...SAGC amplifier, 51...amplitude detection circuit, 61...setup pulse generation circuit.

Claims (1)

[Claims] 1. An information reading head provided corresponding to a plurality of recording tracks, a plurality of amplifiers provided corresponding to each head whose amplification degree can be switched in multiple stages, and an output signal of the amplifier. an amplitude detection circuit provided for each amplifier that detects the amplitude of the amplifier; and a gain control signal generation circuit provided for each amplifier that generates a signal to control the gain of the amplifier according to the output of the amplitude detection circuit. An information reproducing apparatus comprising: means for detecting a difference between a maximum value and a minimum value of the gains of the amplifier set according to the output of the gain control signal generating circuit. Device. 2. Each of the gain control signal generation circuits includes a pulse generation circuit for generating a number of pulses proportional to the detected amplitude at a predetermined timing, and a pulse generation circuit for generating a number of pulses proportional to the detected amplitude at a predetermined timing, and for controlling the gain of the amplifier in response to the generated pulses. The difference detection means receives pulses from the pulse generation circuits in each of the gain control circuits and determines the maximum and minimum number of pulses from each pulse generation circuit. Claim 1 comprising a circuit that detects each value, and a circuit that detects a difference between the outputs of the maximum value detection circuit and the minimum value detection circuit.
The information reproducing device described in Section 1. 3 The maximum value detection circuit comprises an OR circuit into which pulses from each of the pulse generation circuits are input,
The minimum value detection circuit includes an AND circuit into which the pulse from the pulse generation circuit is input, and the difference detection circuit includes the OR circuit, an exclusive OR circuit into which the output pulse of the AND circuit is input, and the exclusive OR circuit. 3. The information reproducing apparatus according to claim 2, further comprising a counter for counting output pulses of a target OR circuit.