DE1164473B - Method for recording and reproducing pulse-coded messages in start-stop operation on or from a magnetic layer memory - Google Patents

Description

Method for recording and playing back pulse-coded messages in start-stop operation on or from a magnetic layer memory for recording Binary-coded information is widely used in magnetic layer memories which the magnetic layer moves relative to the magnetic heads. Among other things are for example magnetic tape storage has become known to the information in several Traces recorded and from which they can be removed again if necessary. In particular In the case of magnetic tape stores, it has proven to be useful to have a separate clock track to be recorded on the magnetic tape indicating where an item of information may be is or can be present on the tape in the other tracks. It depends on then information is read at this point or not, the information content can be 0 or 1 can be determined. According to a particularly advantageous method are offset the pulses of the clock track against the pulses of the individual information tracks, so that they also occurred at different times during the scan. Through this There can be fluctuations in the speed of the magnetic tape and tolerances in the tape speed be balanced in different longitudinal zones.

The individual information elements are then scanned in a dependent manner of the occurrence of the pulses on the clock track. This procedure then enables the recording of the information in the "NRZ procedure" in a particularly simple way (Non-return-to-zero).

It is known that the individual bits of a clock track when scanning a magnetic recording medium to count down to the beginning of a certain storage space to find. The counting result then triggers the scanning of the information, with at Incorrect counting result also requires incorrect control of the storage space is brought about. Furthermore. magnetic recording methods are known, where to use a transverse recording or transverse scanning compared to Direction of travel of a magnetic tape, individual markings are attached, which indicate the individual Set transverse lines on the tape and make a precise mapping between Mark the transverse magnetic cores and the longitudinal tape.

In all known recording methods using a own clock track, which - as known - advantageously in the middle of the magnetic tape is laid, there is still a disadvantage that is that if it fails one or more clock signals the information is garbled and that no criterion is available for when a clock signal has failed. A failure of clock signals can come about, for example, that the magnetic layer at individual points of the tape is irregularly homogeneous or even damaged.

The failure of individual bits (pulses) in other tracks can be known with the help of an error-indicating code or using various Control methods are displayed. This display option does not apply to the Bits of the clock track. But since the advantage of the clock track is only fully effective, even if the failure of one or more clock signals is indicated Need to remedy this disadvantage. According to the invention, this is achieved by that in addition to the clock pulses themselves additional criteria for preferably equal long cycles of these clock pulses are recorded and that by counting the clock pulses of the respective cycle during acceptance, the completeness of the clock pulses is monitored will.

In the memory according to the invention, the individual clock signals summarized in cycles, the clock track being a criterion for the length of each Cycles is pressed. When the clock signals are picked up, they are counted, and the number of clock pulses belonging to the cycle is checked for completeness supervised. If individual clock pulses fail, that of the clock track takes one cycle associated magnetic head correspondingly fewer pulses, which is easily done with the help a simple counter that has the counting capacity the right number of clock pulses within a cycle can be determined.

According to a further development of the concept of the invention, it is particularly advantageous to reverse the clock signals with the "RZ method" (return-to-zero) and the sequence of positive and negative pulses for one cycle each, so that the use of each cycle is achieved through the immediate succession two pulses of the same polarity (phase jump from 1803) is displayed.

Details of the method according to the invention are based on a Embodiment or a pulse diagram explained in detail. The F i G. 1 shows a timing diagram in which the relationships on a magnetic tape store can be described with reference to a clock track. In line a of FIG. 1 is initially reproduced an information signal which is to be fed to a magnetic head by a Control voltage for recording with the »NRZ method« is supplied. As the Can be seen in the representation, the control voltage goes between two information elements 1 does not return to 0.

Line b shows the control voltage for the clock track. At each front and the trailing edge of this control voltage should be sent a clock signal to the magnetic tape the »RZ procedure«. When using the method according to the invention on magnetic tapes, on which information was previously written down, must in order to to ensure an asynchronous overwriting of an aste clock track, first of all a RF deletion can be provided. The corresponding control voltage for the write amplifier, via which the magnetic head for the clock track is supplied with control current is in line c shown. At the times when the magnetization generates 0 in the clock track is to be, the write current changes its polarity so quickly that on the layer no residual magnetization remains.

In a cycle length as shown in line-d, the According to the invention, the polarities of the clock pulses are always reversed so that a clear identification of a cycle length when the clock pulse sequence is decreased is guaranteed. Accordingly, as can already be seen from line c the write current is direct or inverted to the magnetic head to be recorded added. The corresponding magnetization on the layer within the clock track is shown in line e, the signals reproduced in line f when reading supplies, with two read signals as a criterion for the desired cycle occur with the same polarity.

Since the magnetization generated by a current pulse is two Supplies read signals, the number of bits belonging to a cycle must be an even number be. For the same reason, the density requirement for the The clock track is not bigger for the other tracks.

The evaluation of the criterion for each cycle start or for the End of cycle on the left side can be done in different ways. Hereinafter an embodiment is given.

For this embodiment, the read signals are both positive as well as negative polarity are required separately as well as together. A toggle switch then changes to state 1 from the positive read signal and from the negative read signal transferred to state 0. The output voltage of this flip-flop is in line g shown. In addition, a clock pulse train T1 is required for the evaluation, which is delayed by a certain amount from the read clock pulse train. However, this clock pulse sequence T1 is derived from the one that has been read.

These shift clocks T 1 are fed to a counter, each of which according to the number of clock pulses belonging to a cycle, in the selected embodiment after six clock pulses, an output pulse delivers (see line h). Through this A bistable multivibrator is controlled for each pulse, which either emits an output voltage or not (line h in FIG. 1).

The F i g. 2 shows a circuit design as it is used for control a write amplifier can be done via a bistable multivibrator. The den Write amplifier each periodically releasing control voltage acts on the common Switch B on. Depending on which cycle is to be switched through is then the switch D or the switch D is open. At the switch C is a high frequency Erase signal supplied, which erases a possibly recorded signal Guaranteed in the clock track in the times in which the voltage 0 recorded in itself shall be. Depending on the clock input T, the flip-flop R is according to the applied potentials controlled in one position or the other at the correct timing.

The F i g. Fig. 3 shows the device for fault indication as it is is advantageously assigned to a sense amplifier. The error display should be triggered via the flip-flop L in a manner known per se. The tilting stage L is actuated via a plurality of switches if and only if a cycle Contains too few clock pulses. The switches are controlled by voltages in F i g. 1 recorded in detail in the lines marked with the corresponding letters are. It is assumed here that, for example, when in FIG. 1 in line c is a potential different from 0, the input C is turned on while when the potential 0 occurs in line c, the complementary input Z` with potential supplied, so is controlled.

The invention can be modified in various ways. So can the individual control criteria for a cycle of the clock pulses in their own Track or can be obtained by amplitude modulation within the clock pulses. In this case, too, can. then the evaluation by counting the pulses taken within a cycle and comparison with the target number in a manner known per se be monitored. The circuit design, d. H. the structure of the counters and the display device can be dynamic or static in a manner known per se Technique can easily be done in different variations.

Claims (2)

Claims: 1. Method for recording and reproducing pulse-coded messages in start-stop operation on or from a magnetic layer memory, in which the messages are recorded in several tracks and in at least a further track special clock pulses are stored, d u r c h g e -k e n n n z e i c h n e t that except for the clock pulses even additional Criteria for preferably equally long cycles of these clock pulses recorded and that by counting the clock pulses of the respective cycle in the decrease the completeness of the clock pulses is monitored. 2. The method according to claim 1, characterized in that the clock pulses according to the "RZ method" (return-to-zero -Procedure) are recorded, the sequence of the pulse polarities for successive Cycles is reversed. Publications considered: German Auslegeschrift No. 1055 592.