JPS5927980B2 - Defective tape detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for detecting defective magnetic tapes having two or more start end markers.

A magnetic tape for electronic computers is wound onto two reels, and a start end marker (hereinafter referred to as a BOT marker in this specification) and an end marker (hereinafter referred to as an EOT marker in this specification) are provided at both ends of the usable portion. One of each is provided. These BOT and EOT markers are usually made by pasting aluminum foil or silver foil on a predetermined location on the back side of the magnetic layer, and detecting the BOT marker or EOT marker using an optical sensor using a combination of a light emitting diode and a phototransistor. When the magnetic tape is set, the tape is driven by operation on the operation panel until the BOT marker is detected and then stopped. Thereafter, data is continued to be written or read while driving the tape under the control of the tape control device within the central processing unit until the EOT marker is detected. For example, when writing is performed, rewinding is performed once, and when the BOT marker is detected, the tape is stopped there, and the written content can then be read. As mentioned above, only one BOT marker should be provided, but if there are two BOT markers separated by a certain distance due to an error in the manufacturing process, there will be a problem. Even if the writing operation is continued while ignoring the existence of the second BOT marker, when rewinding is performed, it is determined that rewinding ends at the second BOT marker. Therefore, the problem is that the data written between the regular BOT marker and the second marker is lost when read and cannot be used. SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide an apparatus for detecting defective tapes having two BOT markers by electrical means.

Embodiments of the present invention shown in the drawings will be described below.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an operation time chart. In Figure 1, 1-1,
1-2 is a pulse counter, 2-1 and 2-2 are D type flip-flops, 3-1 and 3-2 are JK type flip-flops,
4-1, 4-2, 4-3 are AND circuits, 5-1, 5-2
indicates an OR circuit, and 6 indicates an exclusive OR circuit. Clock A and clock B are the clock pulse application terminals that operate the counter and flip-flop, and C is the terminal that has a slit cut in the capstan for driving the tape and applies the rotation of the capstan as a pulse train using an optical sensor. "Reverse rotation" indicates a terminal to which a signal in each drive direction is applied. When the power is turned on, the counter and flip-flop are all 0'''.

At this time, the magnetic tape is set (autoload). Upon detection of the BOT marker, autoloading ends at time Ts indicated by the downward triangle mark in FIG. At this time, the counter 1-1 treats it as a normal signal when the BOT marker lasts for 1 millisecond or more, since it is possible that what is detected as a BOT marker is caused by scratches on the tape, chatter, etc., and the count value overflows and is output. Clock A to obtain 8F
Adjust the frequency, count value, etc. Flip-flops 2-1, 2-2, and 3-1 are set by the output of ``5F''. Counters 1-2 are then preset. Next, when a normal tape rotation signal is applied, the counter 1-2 receives a pulse from the C terminal and also receives a count enable signal, so it starts counting. In other words, while making sure that the tape is rotating in the normal direction,
When the BOT marker ends, the flip-flop 2-1 is reset and other changes occur. Then, the output of the OR circuit 5-1 becomes "1", passes the first BOT marker, and C
Since the input from the end continues, the counter 1-2 will overcount. This means that the running distance is measured when the tape has finished running up to a predetermined value. The overflow signal of the counter 1-2 is input to the AND circuit 4-3, and when the tape forward rotation signal and the next BOT marker are continuously detected for more than 1 millisecond, an overflow signal of the counter 1-1 is also generated. Therefore, an output is generated in the AND circuit 4-3, the flip-flop 3-2 is set, and a signal indicating that two BOT markers are present is obtained at the output. In other words, the AND circuit 4-3 satisfies both the conditions of measuring the mileage and newly detecting the BOT marker. After auto-loading the magnetic tape, it may start to rotate forward, and then stop and reverse immediately.

At that time, the second BOT marker cannot be detected, so the second
It is preferable that the counter 1-2 is configured as a reversible counter. This is the reason why we provided a [reverse] terminal. In this manner, according to the present invention, ambiguous signals due to scratches on the tape, etc. can be eliminated, and when two BOT markers are electrically detected, it is possible to accurately detect that the tape is defective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an operation time chart of FIG. 1. 1-1, 1-2... Pulse counter, 2-1, 2
2...D type flip-flop, 3-1, 3-2
...JK type flip-flop, 4-1, 4-2
, 4-3...... AND circuit, 5-1, 5-2...
...OR circuit, 6...Exclusive OR circuit.

Claims (1)

[Claims] 1 A first counter that starts counting clock pulses based on a signal that detects a marker pasted on the magnetic tape, outputs a signal by counting for a predetermined period of time, and is reset when the marker is no longer detected. and,
Based on the output signal from the first counter and the condition that the magnetic tape is being driven, a clock pulse count is started and a signal is output by counting the time during which the magnetic tape runs longer than a specified marker length. a second counter, and when the signal of the second counter is output, the first counter
2 on the condition that the signal from the counter is detected.
A defective tape detection device comprising: means for transmitting an error signal when a marker is pasted;