Electrical computers and digital data processing systems: input/ – Input/output data processing – Data transfer specifying
Reexamination Certificate
2000-04-12
2002-07-16
Myers, Paul R. (Department: 2181)
Electrical computers and digital data processing systems: input/
Input/output data processing
Data transfer specifying
C709S200000
Reexamination Certificate
active
06421745
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of transmitting data between two or more devices. More particularly, the present invention relates to the field of transmitting data and controlling data transfer operations between devices over a bus structure.
BACKGROUND OF THE INVENTION
The IEEE standard, “IEEE Std 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. An example of an ideal application for the transfer of data isochronously would be from a video recorder to a television set. The video recorder records images and sounds and saves the data in discrete chunks or packets. The video recorder then transfers each packet, representing the image and sound recorded over a limited time period, during that time period, for display by the television set. The IEEE 1394 serial 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 standard provides a high-speed serial bus for interconnecting digital devices thereby providing a universal I/O connection. The IEEE 1394 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 standard is very thin in size compared to other bulkier cables used to connect such devices. Nodes can be added and removed from an IEEE 1394 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 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 cable. The physical layer
16
also provides arbitration to ensure that all devices coupled to the IEEE 1394 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 acknowledgement 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 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, assignment of the cycle master, assignment of isochronous channel and bandwidth resources and basic notification of errors.
The IEEE 1394 trade association standard, “1394TA IICP Specification for the Instrument & Industrial Control Protocol,” Specification 1.00, Oct. 8, 1999, is an international standard for efficient asynchronous communication to electronic instrumentation and industrial control devices using the IEEE 1394 serial bus. The protocol established by the 1394TA IICP specification uses a dual-duplex plug structure for transfer of data and command/control sequences. According to the 1394TA IICP specification, all communication is flow controlled between a producer device and a consumer device. A producer device is a device that writes data to a consumer device. A consumer device is a device that receives data from a producer device.
A typical 1394TA IICP connection between a computer and an instrument is illustrated in FIG.
2
. The computer
20
is coupled to the instrument
22
by an IEEE 1394-1995 cable. The connection illustrated in
FIG. 2
is a virtual representation of the data flow between the computer
20
and the instrument
22
. The computer
20
includes a connection register
30
and a plug
24
. The instrument
22
includes a connection register
38
and a plug
32
. The connection registers
30
and
38
communicate connection requests and responses related to data transmissions between the plugs
24
and
32
.
The concept of the plugs
24
and
32
and the plug control registers
30
and
38
is used to manage and control the attributes of asynchronous data flows over a 1394TA IICP connection. It should be noted that plugs do not physically exist on a 1394TA IICP device, but the concept of a plug is used to establish an analogy with existing devices where each flow of information is routed through a physical plug.
Each of the plugs
24
and
32
contain a data port and a control port. The plug
24
includes the data port
26
and the control port
28
. The plug
32
includes the data port
34
and the control port
36
. Each port within a plug allows duplex communications with the connected node. Through the data port
26
, the computer
20
, acting as producer, can send data to the instrument
22
, acting as consumer, and can also receive data as a consumer device from the instrument
22
, acting as a producer device. Correspondingly, through the data port
34
, the instrument
22
, acting as producer, can send data to the computer
20
, acting as consumer, and can also receive data as a consumer device from the computer
20
, acting as a producer device.
Control bytes are transferred from either the computer
20
or the instrument, whichever is acting as a producer of control bytes, to the other device, acting as a consumer of control bytes. Control bytes are control messages, interrupts, triggers and commands sent between the devices. The control port within the plug allows the data path to remain a pure data path.
The connection arrangement illustrated in
FIG. 2
is a dual-duplex plug arrangement as both of the plugs
24
and
32
can send data and also include separate data and control ports. Data can also be sent through duplex plugs in which two devices are connected together and either of the devices can send data to the other device. A duplex plug sends data and control information through the same port instead of having separate data and control ports as in the dual-duplex plug arrangement. A simplex operation results if one of the plugs of a connected device does not produce frames and does not have the ability to transmit frame data.
A plug is a data structure including private memory and public memory. The plug private memory includes information necessary in setting up and maintaining a connection, including plug state information about the connected node. The plug public memory is mapped to IEEE 1394 memory space and can be updated by the connected node. To transfer data from a producer device to a consumer device, the consumer device first notifies the producer device through a write operation
Fairman Bruce
James David V.
Shima Hisato
Haverstock & Owens LLP
Myers Paul R.
Sony Corporation
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