Method and apparatus for framing data in a digital transmission line

• US 5,557,614 A
• Filed: 12/22/1993
• Issued: 09/17/1996
• Est. Priority Date: 12/22/1993
• Status: Expired due to Fees

• Current Assignee: VLSI Technology, Inc. (Koninklijke Philips N.V.)
• Original Assignee: VLSI Technology, Inc. (Koninklijke Philips N.V.)
• Inventors: Wingen, Neal T., Sandler, Lorin H.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Nguyen, Chau T.
• Application Number:
  US08/172,458
• Time in Patent Office: 1,000 Days
• Field of Search: 370/84, 370/100.1, 370/105, 370/105.1, 370/106, 370/110.1, 370/105.2, 370/105.4, 370/79, 370/82, 370/112, 375/365, 375/366, 375/368
• US Class Current: 370/509
• CPC Class Codes: H04J 3/0608 Detectors therefor, e.g. correlators, state machines

Abstract

A method and apparatus for framing data in digital transmission lines automatically recognizes a framing format. The apparatus preferably includes a frame alignment apparatus that can recognize any one of a number of predetermined framing formats created by framing information on an input signal. The frame alignment apparatus outputs an aligning signal to an output frame counter, which counts the data and framing information on the input signal and outputs a frame synchronization signal according to the framing format. The input signal is also coupled to an output apparatus that outputs the input signal at the clock rate of a terminating apparatus. The frame alignment apparatus preferably includes a plurality of pattern recognizers able to recognize at least one of the framing formats and a storage apparatus for storing counts of successive data and framing information that match a framing pattern. The counts are preferably used to identify the flaming information on the input signal and the flaming format.

Claims

1. A frame aligment apparatus comprising:

a plurality of pattern recognizers coupled to an input signal, said input signal including data and framing information, wherein at least one of said plurality of pattern recognizers recognizes a pattern of framing information on said input signal that is associated with a recognized framing format, wherein each of said pattern recognizers is operative to recognize a different pattern from said other pattern recognizers, each pattern being associated with at least one of a plurality of different, predetermined framing formats, and wherein each of said plurality of pattern recognizers outputs a count signal;

a storage apparatus coupled to said plurality of pattern recognizers and receiving said count signal from each of said pattern recognizers, said storage apparatus storing a plurality of counts, each count indicating a correspondence of a portion of said data and framing information to one of said different framing formats associated with said count, the values of said counts being based on said count signals; and

a frame controller coupled to said pattern recognizers and receiving a signal from each of said pattern recognizers that is derived from said count signal, said frame controller outputting an indication of said recognized framing format and a frame aligning signal for indicating which of said data and said framing information is framing information.

2. A frame alignment apparatus as recited in claim 1 wherein said pattern recognizers each include at least one state machine programmed to recognize a pattern of framing information corresponding to one of said plurality of different framing formats.

3. A frame alignment apparatus as recited in claim 2 wherein said plurality of pattern recognizers includes pattern recognizers for recognizing patterns corresponding to superframe, extended superframe, T1 data multiplexer, and SLC-96 flaming formats.

4. A frame alignment apparatus as recited in claim 1 wherein each of said plurality of counts stored by said storing apparatus is an amount of data or flaming bits having values that correspond to a pattern associated with at least one of said predetermined framing formats.

5. A frame alignment apparatus as recited in claim 4 wherein said input signal is organized into a pattern of frames forming a plurality of bit streams, wherein each frame includes a plurality of consecutive data bits followed by at least one framing bit, find wherein each of said plurality of counts is associated with one of said bit streams, said counts simultaneously determining which of said bit streams includes said framing bits.

6. A frame alignment apparatus as recited in claim 5 further comprising a comparator for comparing the value of each of said plurality of counts with a predetermined value for each bit of said input signal to recognize one of said plurality of predetermined framing formats, wherein a first of said counts to be incremented to said predetermined value identifies said recognized framing format.

7. A frame alignment apparatus as recited in claim 6 wherein some of said pattern recognizers recognize said pattern over frames of different bit lengths than other pattern recognizers as required by said associated framing formats.

8. A frame alignment apparatus as recited in claim 5 wherein each of said plurality of counts is associated with at least one of said framing formats such that said plurality of counts identify said recognized framing format, and wherein said frame controller outputs a signal indicating said recognized framing format.

9. A frame alignment apparatus as recited in claim 1 wherein each of said count signals includes a current value of an associated count, and wherein said value of said associated count is set to said current value of said count signal.

10. A frame alignment apparatus as recited in claim 1 wherein a particular pattern, when recognized in said data and framing information, identifies at least two different possible framing formats to which said framing information corresponds, such that said frame controller further analyzes said framing information to determine said recognized framing format.

11. A method for framing data on a digital transmission line comprising:

outputting an output signal in accordance with an external output clock, said output signal derived from an input signal, said output signal and said input signal including data and framing information bits;

analyzing said data and framing information bits in said input signal to determine which of said data and framing information bits are framing information bits and to recognize one of a plurality of possible different predetermined framing formats created by said framing information bits in said input signal; and

counting data and framing information bits present on said input signal and outputting a frame synchronization signal in accordance with said output clock when said framing information bits are counted.

12. A method for flaming data as recited in claim 11 wherein said step of analyzing said data and framing information bits and recognizing a framing format includes:

comparing said data and flaming information bits to a plurality of predetermined framing patterns, each of said flaming patterns being associated with at least one of said plurality of framing formats;

storing a plurality of counts, each count indicative of a number of data and flaming information bits corresponding to one of said framing patterns;

utilizing said counts to determine a flaming format to which said framing information bits correspond.

13. A method for flaming data as recited in claim 12 further comprising the step of utilizing said counts to distinguish said framing information bits from said data information bits in said input signal.

14. A method as recited in claim 13 further comprising a step of checking for errors in said framing information bits as compared to said predetermined framing pattern after said recognized framing format has been determined.

15. A method as recited in claim 14 wherein said flaming information bits include signalling information content, and further comprising the step of extracting said signalling information content from said flaming information bits and outputting said signalling information content.

16. A frame alignment apparatus as recited in claim 12 wherein said data and framing information is organized into frames, wherein each frame includes a predetermined number of data and framing bits such that a bit stream is provided for each bit position of said frames, and wherein one of said counts is stored for each of said bit streams of said input signal and for each of said possible predetermined framing formats.

17. A frame alignment apparatus as recited in claim 16 wherein said step of utilizing said counts to determine a framing format includes incrementing a particular one of said counts if a successive bits of said bit stream corresponding to said particular count match said framing pattern, such that a first of said counts to be incremented to a predetermined threshold identifies said recognized framing format and distinguishes said framing bits from said data bits.

18. A frame alignment apparatus as recited in claim 11 wherein an indication of said recognized framing format is output in said outputting step.

19. A digital reception apparatus comprising:

means for receiving data and framing information bits in a digital transmission of information, wherein said data information bits are organized in frames, and wherein said framing information bits designate different frames of said data information bits;

means for determining one of a plurality of possible framing formats from said data and framing information bits by determining which of said data and framing information bits are framing information bits; and

means for outputting said data and framing information bits and a frame synchronization signal, said frame synchronization signal being output when said framing information bits are output which identifies said different frames of said output data information bits.

20. A digital reception apparatus as recited in claim 19 further comprising:

means for receiving data and framing information bits in a plurality of simultaneous digital transmissions, each digital transmission including data and framing information bits; and

a corresponding plurality of said means for outputting, wherein said means for determining one of a plurality of possible framing formats determines a framing format for each of said transmissions.

21. A digital reception apparatus as recited in claim 19 wherein said means for determining one of a plurality of possible framing formats includes means for simultaneously storing a plurality of counts, wherein a count is incremented when an associated bit position in successive frames of said input signal matches a predetermined pattern associated with one of said plurality of framing formats associated with each of said counts.

22. A digitial reception apparatus as recited in claim 21 wherein said means for determining compares values of said counts to a predetermined threshold such that a first of said counts to be incremented to said threshold identifies a framing bit position in said input signal and determines said framing format of said data and framing bits.

23. A method for digital reception comprising:

receiving data and framing bits in a digital transmission;

determining which of said data and framing information bits are framing information bits and recognizing one of a plurality of possible framing formats created by said framing bits; and

outputting an output signal including said data and framing bits and a frame synchronization signal, said frame synchronization signal being output when said framing bits are output in said output signal.

24. A method as recited in claim 23 further comprising:

receiving data and framing bits in a plurality of simultaneous digital transmissions, each digital transmission including data and framing bits; and

outputting at least said data and framing bits and a frame synchronization signal for each of said plurality of transmissions.

25. A method as recited in claim 23 wherein said data and framing information is organized into frames of equal amounts of bits, and wherein said step of determining one of a plurality of possible framing formats includes maintaining a count of bits matched to a pattern associated with one of said framing formats, wherein a plurality of said counts are simultaneously maintained, a separate count being included for each bit position of said frames and for each of a plurality of said possible framing formats.