Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-03-16
2002-04-02
Ton, Dang (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
Reexamination Certificate
active
06366590
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of transmitting information between devices.
More particularly, the present invention relates to the field of providing an interface to applications involved in the transmission of information between devices over a bus or network.
BACKGROUND OF THE INVENTION
The IEEE standard, “1394-1995 Standard For A High Performance Serial Bus,” is an international standard for implementing an inexpensive high-speed serial bus architecture which supports both asynchronous and isochronous format data transfers. Isochronous data transfers are real-time transfers which take place such that the time intervals between significant instances have the same duration at both the transmitting and receiving applications. Each packet of data transferred isochronously is transferred in its own time period. The IEEE 1394-1995 standard bus architecture provides multiple channels for isochronous data transfer between applications. A six bit channel number is broadcast with the data to ensure reception by the appropriate application. This allows multiple applications to simultaneously transmit isochronous data across the bus structure. Asynchronous transfers are traditional data transfer operations which take place as soon as possible and transfer an amount of data from a source to a destination.
The IEEE 1394-1995 standard provides a high-speed serial bus for interconnecting digital devices thereby providing a universal I/O connection. The IEEE 1394-1995 standard defines a digital interface for the applications thereby eliminating the need for an application to convert digital data to analog data before it is transmitted across the bus. Correspondingly, a receiving application will receive digital data from the bus, not analog data, and will therefore not be required to convert analog data to digital data. The cable required by the IEEE 1394-1995 standard is very thin in size compared to other bulkier cables used to connect such devices. 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 will then automatically reconfigure 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 standard defines a protocol as illustrated in FIG.
1
. This protocol includes a serial bus management block
10
coupled to a transaction layer
12
, a link layer
14
and a physical layer
16
. The physical layer
16
provides the electrical and mechanical connection between a device or application and the IEEE 1394-1995 cable. The physical layer
16
also provides arbitration to ensure that all devices coupled to the IEEE 1394-1995 bus have access to the bus as well as actual data transmission and reception. The link layer
14
provides data packet delivery service for both asynchronous and isochronous data packet transport. This supports both asynchronous data transport, using an acknowledgment protocol, and isochronous data transport, providing real-time guaranteed bandwidth protocol for just-in-time data delivery. The transaction layer
12
supports the commands necessary to complete asynchronous data transfers, including read, write and lock. The transaction layer
12
also provides a path for isochronous management data to be transferred to the serial bus management block
10
via read operations with isochronous control compare-swap registers. The serial bus management block
10
contains an isochronous resource manager for managing isochronous data transfers. The serial bus management block
10
also provides overall configuration control of the serial bus in the form of optimizing arbitration timing, guarantee of adequate electrical power for all devices on the bus, assignment of the cycle master, assignment of isochronous channel and bandwidth resources and basic notification of errors.
Data is transferred asynchronously between nodes on the IEEE 1394-1995 serial bus using read, write and lock transactions. Using a read transaction, data at a particular address within a responding node is transferred back to a requesting node. Using a write transaction, data is transferred from a requesting node to a particular address within one or more responding nodes. Using a lock transaction, data is transferred from a requesting node to a responding node, processed with data at a particular address within the responding node and the result is then transferred back to the requesting node.
At the transaction layer level, the read, write and lock transactions each consist of four basic service operations. A request is the basic service operation used by a requesting node to start the transaction. An indication is the basic service operation used to notify the responding node of an incoming request. A response is the basic service operation used by the responding node to return status and possibly data to the requesting node. A confirmation is the basic service operation used to notify the requesting node of the arrival of the corresponding response.
A data flow diagram showing the flow of data to complete a write transaction between two nodes coupled to the IEEE 1394-1995 serial bus is illustrated in FIG.
2
. The transaction layer
20
and the link layer
22
of the node
28
requesting the write transaction and the transaction layer
26
and the link layer
24
of the node
30
responding to the write transaction are shown within FIG.
2
. As illustrated in
FIG. 2
, the write request is sent to the transaction layer
20
of the requesting node
28
from the requesting application. The write request contains the destination address, the write data and the data length for the write operation. A link data request is then sent from the transaction layer
20
to the link layer
22
of the requesting node
28
to begin the transaction. The data to be written at the responding node
30
is then sent from the link layer
22
of the requesting or local node
28
, in a data packet over the IEEE 1394-1995 serial bus, to the link layer
24
of the responding or remote node
30
. A link data indication from the link layer
24
is sent to the transaction layer
26
of the responding node
30
when the link layer
24
receives the data packet from the link layer
22
. Once the link data indication is received by the transaction layer
26
of the responding node
30
, it then sends a write indication to the appropriate application, announcing the arrival of a write request.
Once the write operation has been completed at the responding node
30
, the application to which the data was written sends a write response to the transaction layer
26
of the responding node
30
. The response contains the node_ID of the source node, the transaction label of the corresponding request and the response code. After receiving the write response from the application, the transaction layer
26
then sends a response packet to the link layer
24
of the responding node
30
. The link layer
24
of the responding node
30
then sends an acknowledge packet to the link layer
22
of the requesting node
28
. The link layer
22
of the requesting node
28
, after receiving the acknowledge packet from the link layer
24
, then sends a confirmation to the transaction layer
20
of the requesting node
28
. When the transaction layer
20
of the requesting node
28
receives this confirmation, it sends a write confirmation to the requesting application notifying it that the write operation has been completed.
A data flow diagram showing the flow of data to complete a write split transaction between two nodes coupled to the IEEE 1394-1995 serial bus is illustrated in
FIG. 3. A
split transaction is a transaction where the responding node
30
releases control of the bus after sending an acknowledge signal and then some time later arbitrates for the bus so that it can begin the response subaction. Other subactions may
Haverstock & Owens LLP
Ton Dang
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