DATA RESYNCHRONIZATION EMPLOYING A PLURALITY OF DECODERS

• US 3,860,907 A
• Filed: 06/21/1973
• Issued: 01/14/1975
• Est. Priority Date: 06/21/1973
• Status: Expired due to Term

• Current Assignee: John W. Marshall
• Original Assignee: John W. Marshall
• Inventors: Marshall, John W.
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Malzahn, David H.
• Application Number:
  US05/372,389
• Time in Patent Office: 572 Days
• Field of Search: 340/146.1D,174ED,174DD,174.1B 178/69.5R 179/15AE,15BS
• US Class Current: 714/798
• CPC Class Codes: G11B 20/1809 by interleaving
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00

Abstract

Electrical signals recorded on a magnetic medium as magnetic indicia represent digital data. Digits of data are recorded as encoded pairs of indicia (couples) by corresponding pair of signals. Successive encoded indicia are recorded on the medium serially in sequence; for example, in stripes oriented diagonally across magnetic tape. During reading, defects in the medium, or errors in data transfer, resulting in a loss of synchronization between encoded indicia and the digit represented, are compensated for. Encoded indicia are continuously compared with a resynchronization pattern dispersed throughout recorded data at regular intervals. When an error is detected, the encoded indicia are decoded and stored in two buffers, each storing sets of digits decoded from differently chosen indicia pairs. The contents of one of these buffers is thereafter utilized when a resynchronization pattern identifies the correct set of digits.

Claims

1. In a data subsystem for handling serial sequences of data representative digits, wherein the digits are serially recorded, effectively continuously along physically discontinuous diagonal stripes on an elongated medium, as pairs of adjacent magnetic manifestations corresponding to pairs of electric recording signals, coded to represent the digits in accordance with a predetermined relationship, the recorded digits being sensed by decoding pairs of electric read signals, each pair relating to a single pair of corresponding magnetic manifestations, in accordance with the predetermined relationship;

apparatus effective when electric read signal pairs erroneously relate to noncorresponding magnetic manifestations, comprising;

a shift register having one input for receiving electric read signal pairs in sequence, another input operable to shift the signals in one direction one pair at a time, and a plurality of outputs for supplying the received signals in parallel;

a first and second decoder each having inputs, connected to different sets of the shift register oUtputs, and outputs for supplying digits derived in accordance with the predetermined relationship as a function of the electric read signal pairs at that decoder'"'"''"'"'s inputs;

a first and second memory buffer each having inputs connected to outputs of corresponding ones of the first and second decoders for storing a plurality of digits; and

first and second recognition circuits each having inputs connected to the shift register for receiving electric read signals and outputs supplying signals for selecting for accessing one of said first and second buffers in accordance with the occurrence of digit patterns in the shift register.

2. generating a second series of data digits as a function of a succession of selected adjacent second pairs of signals received at the input, each second pair being offset from the first pair by one signal;

3. In combination:

a source of multi-valued sequential signals, the values of sets of signals representing different digital quantities, and the signals including a periodically occurring predetermined sequence of signals;

a first comparator, having an input connected to the source and an output, for comparing with a predetermined signal sequence a first plurality of sequential signals supplied by the source, and supplying a recognition signal at said output indicative of the reception at the input of said predetermined sequence of signals;

a second comparator, having an input connected to the source and an output for comparing with the predetermined signal sequence a second plurality of sequential signals supplied by the source and supplying a recognition signal at said output indicative of the reception at the input of said predetermined sequence of signals;

decoding means, having an input connected to the source and a plurality of outputs, for supplying at the outputs signals representing digital quantities derived from a number of different groupings of signals sequentially received at the input;

a plurality of buffers equal to the number of comparator outputs each having an input and an output, each input being connected to a different decoding means output and operable to receive for retention in its associated buffer signals representing digital values; and

a gating circuit, connected to the comparator and buffer outputs for accessing those signals representing digital values retained in that buffer which corresponds to the comparator output supplying a recognition signal.

4. generating selection signals for accessing one of the series of data digits in accordance with the predetermined synchronism sequence received at the input;

and

5. In a system wherein data digits, initially encoded into sIgnal sets in a sequence of multivalued signals, are received at an input and decoded as data digits;

apparatus for correlating the selection of sets of the signals received at the input with the corresponding signal sets as initially encoded, comprising;

first decoding means, connected to the input via intervening means, for generating a first series of data digits as a function of a succession of selected adjacent first sets of the signals received at the input;

second decoding means, connected to the input via intervening means, for generating a second series of data digits as a function of a succession of selected adjacent second sets of the signals received at the input;

first and second accessible storage means, connected with respective ones of the first and second decoding means, for storing data digits generated by the corresponding decoding means;

selection means, connected to the input, operable in accordance with a predetermined portion of the sequence of signals received at the input to generate selection signals used for accessing one of the storage means; and

output means, connected with the storage means and the selection means, for transferring to an output, in accordance with the selection signals, data digits from the storage means selected by the selection means.

6. The apparatus of claim 5 wherein:

the sequence of signals received at the input includes synchronism portions, each portion comprising a succession of predetermined signal values.

7. The apparatus of claim 5 wherein:

the second sets of selected adjacent signals received at the input are offset from the first sets by one signal.

8. The apparatus of claim 7 wherein:

the sequence of signals received at the input includes synchronism portions, each portion comprising a succession of predetermined signal values.

9. The apparatus of claim 8 wherein:

the selection means generates a first selection signal when the synchronism portion of the sequence of signals received at the input is identified with the first sets of the received signals and generates a second selection signal when the synchronism portion is identified with the second sets.

10. Apparatus for correlating the selection of groups of the signals received at an input with the corresponding signal groups as initially encoded, comprising:

decoding means, connected to the input through intervening means, for generating a plurality of series of data digits as a function of a succession of a plurality of selected adjacent sets of the signals received at the input;

means;

plurality of storage means, connected with the decoding means, each for storing one series of the plurality of series of data digits generated by the decoding mans;

selection means, connected to the input, operable in accordance with a predetermined portion of the sequence of signals received at the input to generate selection signals used for accessing one of the plurality of storage means; and

output means, connected with the storage means and the selection means, for transferring to an output, in accordance with the selection signals, data digits from the storage means selected by the selection means.

11. In a data processing system including:

A. a source of sequential electric signals, adjacent multiples of which signals represent digital values originally supplied to the source in accordance with a preassigned code, including a periodic sequence of predetermined signals representing a synchronization pattern;

B. more than one utilization means, connected to the source, each interpreting successive multiples of signals received from the source as unique digit values in accordance with the preassigned code and without regard to external perturbations which might cause the signal multiples received by the utilization means to differ from those originally supplied to the source; and

C. means for compensating for interpretation errors introduced by the perturbations, includiNg;

12. In a data processing system for retrieving digital data recorded as magnetic indicia on a magnetic media, wherein signal couples representing magnetic indicia are encoded from corresponding digits of data and the signals periodically include a known predetermined pattern;

a combination for maintaining the correspondence of couples and digits despite the temporary failure, during retrieval, to properly receive all the signals, comprising;

a first and second decoder, each having an input and an output, for supplying at each output first digits of data derived from respective first and second signal pairs representing magnetic indicia received at the corresponding input;

first and second storage means, each having an input and an output, the inputs being connected to outputs of corresponding ones of the first and second decoders, for storing digits of data received therefrom;

recognition means, having an input and an output, for indicating as a signal at the output the presence at the input of said known predetermined pattern of digits in alignment with specified ones of the first and second signal pairs; and

gating means connected to said first and second storage means and to said recognition means for transferring to an output the digits of data stored in a selected one of said storage means in response to the signals at the output of said recognition means.

13. In combination:

a source of sequential binary signals, the binary values of pairs of signals representing different digital quantities, and the signals including a periodically occurring predetermined sequence of synchronization signals;

a first comparator, having an input connected to the source and an output, for comparing with a representation of the synchronization signals a first plurality of sequential signals supplied by the source, and supplying a recognition signal at said output indicative of the reception at the input of said synchronization signals;

a second comparator, having an input connected to the source and an output for comparing with a representation of the synchronization signals a second plurality of sequential signals supplied by the source and supplying a recognition signal at said output indicative of the reception at the input of said predetermined sequence of signals;

decoding means, having an input connected to the source and first and second outputs, for supplying at the outputs signals representing digital quantities derived from different pairs of signals sequentially received at the input;

a plurality of buffers equal to the number of comparator outputs each having an input and an output, each input being connected to a different decoding means output and operable to receive for retention in its associated buffer signals representing digital values; and

a gating circuit, connected to the comparator and buffer outputs for accessing those signals representing digital values retained in that buffer which corresponds to the comparator output supplying a recognition signal.

14. The combination of claim 13 wherein the second plurality of synchronization signals differs from the first plurality by one signal.

15. In a system wherein data digits, initiAlly encoded into couples in a sequence of binary signals including a predetermined synchronism sequence, are received at an input and decoded as data digits;

apparatus for correlating the selection of couples received at the input with the corresponding couples initially encoded, comprising;

first decoding means, indirectly connected with the input, for generating a first series of data digits as a function of a succession of selected adjacent first pairs of signals received at the input;

second decoding means, indirectly connected with the input, for generating a second series of data digits as a function of a succession of selected adjacent second pairs of signals received at the input, each second pair being offset from the first pair by one signal;

first and second accessible storage means, connected to respective ones of the first and second decoding means, for storing data digits generated by the corresponding decoding means;

selection means, connected with the input, operable in accordance with the predetermined synchronism sequence received at the input to generate selection signals usable for accessing one of the storage means; and

output means, connected with the storage means and the selection means, for transferring to a utilization device, in accordance with the selection signals, data digits from the storage means selected by the selection means.

16. The apparatus of claim 15 wherein:

the selection means generates a first selection signal when the synchronism portion of the sequence of signals received at the input is identified with the first sets of the received signals and generates a second selection signal when the synchronism portion is identified with the second sets.

17. In a data processing system, including:

a source of sequential electric signals, adjacent couples of which signals represent digital values originally supplied to the source in accordance with a preassigned code, said signals including a periodic sequence of predetermined synchronization signals;

a plurality of utilization means, connected to the source, each for interpreting successive couples of signals received from the source as unique digit values in accordance with the preassigned code and without regard to external perturbations which might cause the signal multiples received by the utilization means to differ from those originally supplied to the source;

memory units connected to the utilization means, each unit storing a plurality of manifestations of the digital values from a corresponding utilization means, and operable to release stored manifestations; and

recognition means, having one input connected to the source and a different output connected to each memory unit, for monitoring the signals received from the source and identifying the occurrence of a synchronization pattern by placing a signal on one output, to operate the connected memory to release stored manifestations, as a function of the difference between the adjacent couples originally supplied to the source and those received therefrom.

18. In a system wherein data digits, initially encoded into signal sets in a sequence of multi-valued signals, are received at an input and decoded as data digits;

a method for correlating the selection of sets of the signals received at the input with the corresponding signal sets as initially encoded, comprising the steps of;

generating a first series of data digits as a function of a succession of selected adjacent first sets of the signals received at the input;

generating a second series of data digits as a function of a succession of selected adjacent second sets of the signals received at the input;

storing generated data digits;

generating selection signals for accessing one of the series of data digits in accordance with a predetermined portion of the sequence of signals received at the input; and

accessing, in accordance with the selection signals, the selected data digits.

19. In a system wherein data digits, initially encoded into couples in a sequence of binary signals including a predetermined synchronism sequence, are received at an input and decoded as data digits;

a method for correlating the selection of couples received at the input with the corresponding couples initially encoded, comprising the steps of;

20. The method of claim 19 wherein step (4) is further defined as:

generating a first selection signal, when the synchronism portion of the sequence of signals received at the input is identified with the first sets of the received signals, and generating a second selection signal when the synchronism portion is identified with the second sets.

21. A method for correlating the selection of groups of the signals received at an input with the corresponding signal groups as initially encoded, comprising the steps of:

generating a plurality of series of data digits as a function of a succession of a plurality of selected adjacent sets of the signals received at the input;

storing each series of the plurality of series of data digits generated;

generating selection signals for accessing one of the plurality of series of stored data digits in accordance with a predetermined portion of the sequence of signals; and

accessing, in accordance with the selection signals, the selected data digits.

22. In a system transmitting and receiving a series of data signals with interleaved synchronization signals, apparatus for resynchronizing the phase of signals received prior to the loss of synchronism, comprising:

data decoding means, having inputs and a plurality of outputs, for supplying to the plurality of outputs data decoded as a plurality of functions of the data received at the inputs;

a plurality of stores, each having an input, connected to a corresponding decoding means output, and an output, each store operable to store decoded data supplied at one of the decoding means outputs;

synchronization recognition means, having inputs and a plurality of outputs, for recognizing synchronization signals received at the inputs and supplying to separate ones of the outputs an indication of the synchronization phase; and

means connected to the stores and the synchronization recognition means for accessing via the output of the one of the stores, corresponding to the synchronized recognition means output having a phase indication, the decoded data therein.

23. In combination:

means for supplying a sequence of signals including data representative signals;

first means connected with the supply means for storing a first function of data representative signals;

second means connected with the supply means for storing a second function of aforesaid data representative signals;

recognition means connected with the supply means for monitoring additional signals interleaved in said sequence of signals and indicating the one of the first and second functions represented thereby; and

gating means, connected with the first and second means and the recognition means, operable in accordance with the function indicated by the recognition means to access data from the one of the first and second means storing data in accordance with the corresponding function.