Frame-based transmission of data

• US 5,361,261 A
• Filed: 11/02/1992
• Issued: 11/01/1994
• Est. Priority Date: 11/02/1992
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Edem, Brian C., Worsley, Debra J.
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US07/970,329
• Time in Patent Office: 729 Days
• Field of Search: 370/60, 370/79, 370/80, 370/82, 370/84, 370/85.1, 370/85.2, 370/85.3, 370/85.7, 370/94.1, 370/94.2, 370/110.1, 370/110.4, 370/111, 370/112, 370/118, 370/97, 358/11-14, 358/133, 358/141, 358/142, 358/146, 341/51, 341/52, 341/60, 341/67, 341/68, 341/70, 341/76, 341/95, 341/102
• US Class Current: 370/445
• CPC Class Codes: H04L 12/44 Star or tree networks
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/6437 Ring
• CPC Class Codes: H04L 2012/6448 Medium Access Control [MAC]
• CPC Class Codes: H04L 2012/6459 Multiplexing, e.g. TDMA, CDMA

Abstract

A network for transferring packet data in a frame structure, preferably mixed with isochronous data is provided. The frame structure is a continuously repeating structure, with each frame having a number of time slots. Certain ones of the time slots are available for transmitting packet data. The packet data is re-timed, e.g., by using a FIFO to output the data nibble-wise as required by the frame structure. Similar re-timing can be used for isochronous data so that the frame structure defines time-division multiplexing of the packet data and isochronous data. A four/five encoding scheme provides sufficient encoding efficiency that both the packet data and other data can be accommodated without degrading the data rate of the packet data. The encoding scheme provides extra symbols which can be used for transferring "no carrier" information, or "frame alignment" messages. Preferably, the frame structure is translated to and from a packet structure to permit the present invention to be used with previously available packet circuitry such as a media access controller and a hub repeater circuit. Latency of the FIFO can be reduced by pre-filling with packet preambles, and/or sub-latency propagation of preamble bytes, or providing special MACs which do not output preambles, and using the buffer circuitry to output preambles.

Claims

1. Apparatus for conveying data from a data source, over physical media, to a data sink, said data source including a media access controller which outputs first data in a packet form, the apparatus comprising:

a first buffer, coupled to said media access controller for receiving said first data in packet form and outputting at least said first data as a first plurality of groups of bits of said first data;

a first encoder for receiving and encoding at least said first data and outputting encoded data;

a clock-responsive transmitter coupled to said encoder for receiving said encoded data and coupled to said physical media for transmitting said encoded data onto said physical media,

a reference clock, coupled to said transmitter, for establishing the beginning times of a plurality of contiguous time frames, each time frame having a plurality of time slots,

wherein each of said first plurality of groups of bits is transmitted by said transmitter during a first set of predetermined ones of said time slots, at least some of said first set of predetermined ones of said time slots being non-contiguous.

2. Apparatus, as claimed in claim 1, further comprising:

an isochronous data source outputting isochronous data;

a second buffer for receiving said isochronous data and outputting a second plurality of groups of bits of said isochronous data;

said transmitter coupled to said second buffer for receiving said second plurality of groups of bits of said isochronous data wherein each of said second plurality of groups of bits is transmitted by said transmitter onto said physical media during a second set of predetermined ones of said time slots, said second set being different from said first set wherein the data placed on said physical medium during at least one of said time frames includes both said encoded data, originating from said media access controller and said second plurality of groups of bits, originating from said isochronous data source.

3. Apparatus, as claimed in claim 2, wherein said transmitter transmits said second plurality of bit groups at a second effective bandwidth of about 6.144 Mb/sec.

4. Apparatus, as claimed in claim 1, wherein said media access controller is an Ethernet media access controller.

5. Apparatus, as claimed in claim 1, wherein said first outputs said encoded data in a first encoded form according to a 4/5 encoding scheme wherein 4 bits are encoded into a 5-bit group.

6. Apparatus, as claimed in claim 5, wherein said first encoder includes an NRZI encoder.

7. Apparatus, as claimed in claim 1, wherein each of said first plurality of groups of data bits includes the same number of bits.

8. Apparatus, as claimed in claim 7, wherein said number of bits is 4.

9. Apparatus, as claimed in claim 1, wherein said transmitter transmits said first plurality of bit groups at a first effective bandwidth of about 10 Mb/sec.

10. Apparatus, as claimed in claim 1, wherein said first buffer comprises a first-in-first-out memory.

11. Apparatus, as claimed in claim 1, wherein

said media access controller outputs a carrier signal during at least a first time period, does not output said carrier signal during at least a second time period which occurs after said first time period and outputs said carrier signal during a third time period which occurs after said second time period, and wherein

said first encoder outputs at least a third bit group in response to receipt of the media access controller output which occurs during said second time period, said third bit group being different from any of the bit groups output by the first encoder during said first and third time periods, to provide a no-carrier indication.

12. Apparatus, as claimed in claim 1, wherein said data sink includes output circuitry and a repeater for conveying said encoded data to said output circuitry, said repeater, configured to receive said encoded data at a first data rate and further comprising:

a buffer in said data sink, different from said first buffer, for receiving said encoded data from said physical media, and outputting said encoded data at said first data rate to said repeater.

13. Apparatus, as claimed in claim 1, wherein said data sink is a hub of a star-topology network and said data source is a node of said star-topology network.

14. Apparatus for conveying data from a data source, over physical media, to a data sink, said data source including a media access controller which outputs first data in a packet form, the apparatus comprising:

a first buffer, coupled to said media access controller for receiving said first data in packet form and outputting at least said first data as a first plurality of groups of bits of said first data;

a first encoder for receiving and encoding at least said first data and outputting encoded data;

a clock-responsive transmitter coupled to said first encoder for receiving said encoded data and coupled to said physical media for transmitting said encoded data onto said physical media,

a reference clock, coupled to said transmitter, for establishing the beginning times of a plurality of contiguous time frames, each time frame having a plurality of time slots,

wherein each of said first plurality of groups of bits is transmitted by said transmitter during a first set of predetermined ones of said time slots, at least some of said first set of predetermined ones of said time slots being non-contiguous;

wherein said first encoder outputs said encoded data in a first encoded form according to a 4/5 encoding scheme wherein 4 bits of data are encoded into a 5-bit group;

wherein said data sink includes a repeater for said first data, configured to receive said first data in a second encoded form and further comprising;

a second encoder, different from said first encoder, in said data sink for encoding said first data in said second encoded form.

15. Apparatus, as claimed in claim 14, wherein said second encoded form is differential manchester encoding.

16. Apparatus for conveying data from a data source, over physical media, to a data sink, said data source including a media access controller which outputs first data in a packet form, the apparatus comprising:

a first buffer, coupled to said media access controller for receiving said first data in packet form and outputting at least said first data as a first plurality of groups of bits of said first data;

a first encoder for receiving and encoding at least said first data and outputting encoded data;

a clock-responsive transmitter coupled to said first encoder for receiving said encoded data and coupled to said physical media for transmitting said encoded data onto said physical media,

a reference clock, coupled to said transmitter, for establishing the beginning times of a plurality of contiguous time frames, each time frame having a plurality of time slots,

wherein each of said first plurality of groups of bits is transmitted by said transmitter during a first set of predetermined ones of said time slots, at least some of said first set of predetermined ones of said time slots being non-contiguous;

wherein said media access controller which outputs said first data in a packet form outputs a first indication of the beginning of a packet, outputs a first number of data bits after said output of said first indication and outputs an indication of the end of a packet, after said output of said first number of data bits and further comprising;

means for determining whether said first number of data bits is divisible evenly by a predetermined integer and for outputting a frame alignment signal if said first number of data bits is not divisible evenly by said predetermined integer.

17. Apparatus, as claimed in claim 16, wherein said predetermined integer is 4.

18. Apparatus, as claimed in claim 16, wherein said frame alignment signal is transmitted during one of said first set of said predetermined ones of said time slots.

19. Apparatus for conveying data from a data source, over physical media, to a data sink, said data source including a media access controller which outputs first data in a packet form, the apparatus comprising:

a first buffer, coupled to said media access controller for receiving said first data in packet form and outputting at least said first data as a first plurality of groups of bits of said first data;

a first encoder for receiving and encoding at least said first data and outputting encoded data;

a clock-responsive transmitter coupled to said first encoder for receiving said encoded data and coupled to said physical media for transmitting said encoded data on said physical media,

a reference clock, coupled to said transmitter, for establishing the beginning times of a plurality of contiguous time frames, each time frame having a plurality of time slots,

wherein each of said first plurality of groups of bits is transmitted by said transmitter during a first set of predetermined ones of said time slots, at least some of said first set of predetermined ones of said time slots of being non-contiguous;

wherein said media access controller outputs a preamble comprising at least one preamble symbol prior to outputting at least said first data and, and wherein said first buffer requires at least a first latency period between initial receipt of said first data and beginning output of said first data; and

said first buffer including circuitry for distinguishing said preamble symbol from said first data and for outputting said preamble symbol a second period after receipt of said preamble symbol, said second period being less than said first latency period.

20. Apparatus for conveying data from a data source, over physical media, to a data sink, said data source including a media access controller which outputs first data in a packet form, the apparatus comprising:

a first buffer, coupled to said media access controller for receiving said first data in packet form and outputting at least said first data as a first plurality of groups of bits of said first data;

a first encoder for receiving and encoding at least said first data and outputting encoded data;

a clock-responsive transmitter coupled to said first encoder for receiving said encoded data and coupled to said physical media for transmitting said encoded data onto said physical media,

a reference clock, coupled to said transmitter, for establishing the beginning times of a plurality of contiguous time frames, each time frame having a plurality of time slots,

wherein each of said first plurality of groups of bits is transmitted by said transmitter during a first set of predetermined ones of said time slots, at least some of said first set of predetermined ones of said time slots being non-contiguous;

wherein said media access controller outputs a preamble comprising at least one preamble symbol prior to outputting at least said first data and, and wherein said first buffer requires at least a first length of data to be input before beginning output of said data; and

said first buffer including circuitry for extending said preamble by repeating the output of said preamble symbol at least until said first length of said first data has been input into said first buffer.

21. Apparatus for conveying data from a data source, over physical media, to a data sink, said data source including a media access controller which outputs first data in a packet form, the apparatus comprising:

a first buffer, coupled to said media access controller for receiving said first data in packet form and outputting at least said first data as a first plurality of groups of bits of said first data;

a first encoder for receiving and encoding at least said first data and outputting encoded data;

a clock-responsive transmitter coupled to said first encoder for receiving said encoded data and coupled to said physical media for transmitting said encoded data onto said physical media,

a reference clock, coupled to said transmitter, for establishing the beginning times of a plurality of contiguous time frames, each time frame having a plurality of time slots,

wherein each of said first plurality of groups of bits is transmitted by said transmitter during a first set of predetermined ones of said time slots, at least some of said first set of predetermined ones of said time slots being non-contiguous;

wherein said media access controller does not output a preamble prior to outputting said first data; and

said first buffer includes circuitry for generating and outputting at least one preamble symbol prior to outputting said first data.

22. A method for transmitting both data from a packet source and data from an isochronous source onto a physical medium comprising:

transmitting signals onto said physical medium during a first time frame, said frame comprising a predetermined number of time slots, according to a first frame structure defining first and second pluralities of time slots wherein

said first plurality of said time slots is used for transmission of a first plurality of symbols in response to said isochronous data source, each of said first plurality of symbols comprising a plurality of bit-groups, each for conveying a first predetermined number of data bits, and

said second plurality of said time slots being used for transmission of a second plurality of symbols in response to said packet source, said second plurality of symbols comprising at least a first bit-group for transmission in response to a period of non-output of a packet from said packet source and a plurality of bit-groups, different from said first bit-group, each for conveying a first predetermined number of data bits in response to output of a packet from said packet source,

repeating said step of transmitting, during subsequent time frames, at regular time intervals, according to said first frame structure.

23. Apparatus for transmitting both data from a packet source and data from an isochronous source onto a physical medium comprising:

means for transmitting signals onto said physical medium during a first time frame, said frame comprising a predetermined number of time slots, according to a first frame structure defining first and second pluralities of time slots wherein

said first plurality of said time slots is used for transmission of a first plurality of symbols in response to said isochronous data source, each of said first plurality of symbols comprising a plurality of bit-groups, each for conveying a first predetermined number of data bits, and

said second plurality of said time slots being used for transmission of a second plurality of symbols in response to said packet source, said second plurality of symbols comprising at least a first bit-group for transmission in response to a period of non-output of a packet from said packet source and a plurality of bit-groups, different from said first bit-group, each for conveying a first predetermined number of data bits in response to output of a packet from said packet source,

means for repeating the transmitting of signals by said means for transmitting, during subsequent time frames, at regular time intervals, according to said first frame structure.