Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data transfer regulating
Reexamination Certificate
1999-02-01
2002-03-26
Dinh, Dung C. (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data transfer regulating
C709S249000, C709S250000, C710S107000, C710S108000
Reexamination Certificate
active
06363428
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of communicating packetized data between network node devices. More particularly, the present invention relates to the field of communicating packetized data between network node devices in an IEEE 1394-1995 serial bus network.
BACKGROUND OF THE INVENTION
A standard adopted by the Institute for Electrical and Electronics Engineers (IEEE), “IEEE 1394-1995 Standard For A High Performance Serial Bus,” is an international standard for implementing an economical high-speed serial bus architecture. This standard provides a universal input/output connection for interconnecting digital devices including, for example, audio-visual equipment and personal computers.
The IEEE 1394-1995 standard supports both asynchronous and isochronous format data transfers. Asynchronous transfers are data transfer operations which transfer data from a source node to a destination node and take place as soon as permitted after initiation. An example of an application appropriate for asynchronous data transfer is communication of a still image or text document. Control commands can also be sent asynchronously.
Isochronous data transfers are real-time data transfers which take place such that time intervals between significant instances have the same duration at both the transmitting and receiving applications. An example of an application suitable for the transfer of data isochronously is the transfer of audio-visual data (AV data) between devices, such as a video camera and a television set. The video camera records sounds and images (AV data) and stores the data in discrete segments on tape. Each segment represents the image and/or sound recorded over a limited period of time. The video camera then transfers each segment in a packetized manner during an appropriate interval for reproduction by the television set.
The IEEE 1394-1995 standard bus architecture provides multiple channels for isochronous data communication between applications. A six-bit channel number is broadcast with the data to allow reception by the appropriate application. This allows multiple applications to concurrently communicate isochronous data across the bus structure without interfering with each other.
The cable required by the IEEE 1394-1995 standard is relatively thin in size compared to other bulkier cables used to connect such devices. The IEEE 1394-1995 cable environment is a network of nodes connected by point-to-point links, each link including a port for each node's physical connection and the cable between them. The physical topology for the cable environment of an IEEE 1394-1995 serial bus is a non-cyclic network of multiple ports, with finite branches. A primary restriction on the cable environment is that nodes must be connected together without forming any closed loops.
Devices can be added and removed from an IEEE 1394-1995 bus while the bus is active. If a device is so added or removed, the bus automatically reconfigures itself for transmitting data between the then existing nodes. A node is considered a logical entity with a unique address on the bus structure. Each node provides an identification ROM, a standardized set of control registers and its own address space.
The IEEE 1394-1995 cables connect ports together on different nodes. Each port includes terminators, transceivers and logic. A node can have multiple ports at its physical connection. The cable and ports act as bus repeaters between the nodes to simulate a single logical bus. The cable physical connection at each node includes one or more ports, arbitration logic, a resynchronizer and an encoder. Each of the ports provide the cable media interface into which the cable connector is connected. The arbitration logic provides access to the bus for the node. The resynchronizer takes received data-strobe encoded data bits and generates data bits synchronized to a local clock for use by the applications within the node. The encoder takes either data being transmitted by the node or data received by the resynchronizer, which is addressed to another node, and encodes it in data-strobe format for transmission across the IEEE 1394-1995 serial bus. Using these components, the cable physical connection translates the physical point-to-point topology of the cable environment into a virtual broadcast bus, which is expected by higher layers of the system. This is accomplished by taking all data received on one port of the physical connection, resynchronizing the data to a local clock and repeating the data out of all of the other ports from the physical connection.
Each isochronous data packet includes at least a 1394 packet header. The packet header includes overhead information necessary for proper communication of the packet. Typically, content data, such as audio-visual data, is included in the packet, in a data field following the packet header. When an isochronous data packet is received, the receiving device must generally separate the header information from the content data so that the content data can be appropriately processed, such as for display. In addition, due to timing considerations, isochronous packets which include only header information and no content data portion are occasionally communicated via an IEEE 1394-1995 bus. The data field may contain a header and audio-visual content data, as when the CIP Transport Protocol is used. This header within the data field is the CIP header. For CIP transport, some data fields contain only the CIP header. This use of a header and data protocol within the data field is referred to as an Isochronous Transport Protocol. A receiver of such isochronous packets cannot necessarily predict when a packet will not include a content data portion until after the 1394 header information is received.
This can cause errors in the processing of isochronous data packets at the receiving device. For example, if the receiving device receives an isochronous data, packet with only a header and no content data portion, but expected the packet to include a data portion, the receiving device will typically process the header portion properly. When the next data packet is received, however, the receiving device will process the header portion for this next packet as content data because the receiving device expected the next received information to be the content data portion of the prior packet.
SUMMARY OF THE INVENTION
The invention is an apparatus for and method of separating protocol header information contained in the data field from content data in an IEEE 1394-1995 serial bus network. A receiving node receives isochronous data packets from a transmitting node of such packets via an IEEE 1394-1995 serial bus. Within the data field, each packet can include a data portion in addition to protocol header information, although not every packet necessarily includes the data portion. The receiving node cannot necessarily predict when a packet does not include a data portion with audio-visual content until after at least a portion of a 1394 packet including the header is received.
Each incoming packet is loaded into a first-in, first-out, (FIFO) buffer in the receiving node as the packet is being received. The protocol header information within the data field is removed and stored in sequence in a first block of memory. This is accomplished by placing an input_more direct memory access (DMA) instruction into a next instruction register and, then, executing the instruction. An address for storing each protocol header is maintained by incrementing an address utilized for storing a previous protocol header an amount corresponding to the length of the previous header. In the preferred embodiment, each protocol header within the data field has an expected length of eight bytes.
In addition, the receiver is conditioned for removing the data portion from the FIFO buffer. This is accomplished by loading an input_last DMA instruction into the next instruction register. If examination of the 1394 header information reveals that the data field includes audio-visual dat
Chou Chen-Chi
Fairman Bruce
Dinh Dung C.
Haverstock & Owens LLP
Ho Chuong
LandOfFree
Apparatus for and method of separating header information... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for and method of separating header information..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for and method of separating header information... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2850084