Communications: electrical – Selective – Monitoring in addition to control
Reexamination Certificate
1999-06-04
2004-04-27
Holloway, III, Edwin C. (Department: 2635)
Communications: electrical
Selective
Monitoring in addition to control
C340S003700, C340S870030, C340S870030
Reexamination Certificate
active
06727799
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for performing communication among a plurality of electronic equipments connected with one another by means of communication control buses capable of transmitting a control signal and an information signal included therein such as a serial bus conforming to IEEE-1394 for instance (hereinafter referred to as an IEEE 1394 serial bus), and more particularly to a communication control method and electronic equipments that eliminate useless communication and also make control easier when electronic equipments control the operation of other electronic equipments.
2. Description of Related Art
A system in which a plurality of electronic equipments are connected with one another by means of communication control buses capable of transmitting a control signal and an information signal included therein such as an IEEE 1394 serial bus and the information signal and the control signal are communicated among these electronic equipments is being considered.
FIG. 9
shows an example of such a system. This system is provided with a hard disk unit
1
, a personal computer
2
, a television receiver (hereinafter referred to as a TV)
3
, a video tape recorder (hereinafter referred to as a VTR)
4
, and a set top box
5
. Further, the hard disk unit
1
and the personal computer
2
, the personal computer
2
and the VTR
4
, the VTR
4
and the TV
3
, and the VTR
4
and the set top box
5
are connected with each other by means of IEEE 1394 serial buses
6
to
9
, respectively. Here, #A to #E represent node IDs on the system of the hard disk unit
1
, the personal computer
2
, the TV
3
, the VTR
4
and the set top box
5
, respectively.
Transmission of a signal in respective electronic equipments (hereinafter referred to as equipments) within the system is performed by time division multiplexing at every predetermined communication cycle (125 &mgr;sec for instance) as shown in FIG.
10
. The signal transmission is started when an electronic equipment called a cycle master sends out a cycle start packet showing the starting time of a communication cycle onto the bus.
The configuration of communication in one communication cycle includes two types, one being Iso communication for transmitting an information signal such as video data and audio data isochronously (hereinafter “isochronous” is abbreviated as “Iso”) and the other being Async communication for transmitting a control signal such as a control command asynchronously (hereinafter “asynchronous” is abbreviated as “Async”). Further, an Iso communication packet is transmitted before an Async communication packet. It is possible to make a distinction among a plurality of Iso data by assigning channel numbers,
1
,
2
,
3
, . . . , n to respective Iso communication packets. After transmission of the Iso communication packet is completed, the period until a next cycle start packet is used for transmitting the Async communication packet.
In the Async communication, a control signal used by a certain equipment when it makes a demand for something to another equipment is called a command, and the side of sending this command being included in a packet is called a controller. Further, the side of receiving the command is called a target. The target sends a packet holding a control signal showing the result of execution of a command (which is called a response) back to the controller as occasion demands.
These command and response are communicated between one controller and one target, and a series of exchanges that are started with transmission of the command and completed with sending back of the response are called command transaction. It has been decided that the target has to return a response as quickly as possible (for example, within 100 ms) after the command is received. The reason for the above is to prevent stagnation of processing when the controller side continues to wait for the response for long and processing is delayed or the response has not been returned because of some obstacle or other.
The controller can make a demand to perform specific action to the target or inquire after the present state of the target. Any equipment in the system can start and terminate the command transaction. Namely, any equipment can act either as a controller or as a target.
FIG. 11
shows a construction of an Async communication packet including a control signal. Both the command and the response have the same construction. In
FIG. 11
, the data of a packet are transmitted sequentially from top to bottom and left to right.
The packet is composed of a packet header and a data block. Further, standards of all of the packet headers and the data CRC in the data block, that is, the portion applied with halftone have been determined by IEEE 1394, and the contents of the data block are written from an equipment shown by source ID of the packet header to an address shown in destination offset of the equipment shown by the destination ID.
In
FIG. 9
for instance, when a command is sent from the personal computer
2
to the VTR
4
, the source ID, the destination ID and the destination offset are memory spaces that have been allotted as #B, #D and the area for storing the command in VTR
4
, respectively. When it is desired that the personal computer
2
transmits a command to all of the other equipments in the system, 16 bits of the destination ID are set to “all 1”. This communication configuration is called broadcast.
In the data block shown in
FIG. 11
, CTS (command transaction set) shows the type of command language. Further, CT/RC (command type/response code) shows the type of demand in the case of a command, and shows the type of reply to the demand in the case of a response. HA (header address) shows whether the other party for which a demand is made is the whole equipments or it is a subdevice (a functional unit) within the equipments in the case of a command, and HA is the same as the corresponding command in a sense that the other party replies in the case of a response. OPC (operation code) shows a command code, i.e., a concrete demand, and parameters required for the demand are shown with an OPR (operand) following OPC.
FIG. 12
shows a structure of a portion for making exchanges of a command and a response described above taking the VTR among the equipments within the system as an example. This VTR is provided with a VTR device
11
and an IEEE 1394 bus transmission-reception block
12
.
The VTR device
11
is composed of a microcomputer, and is provided with a VTR subdevice
13
for performing processing of commands and so on related to a recording/playback system (not shown) within the VTR, a tuner subdevice
14
for performing processing of commands and so on related to a tuner (not shown) within the VTR, and a timer subdevice
15
for performing processing of commands and so on related to a timer (not shown) within the VTR. These subdevices are formed of softwares of the microcomputer.
The IEEE 1394 bus transmission-reception block
12
detects an Async communication packet received through the bus, and sends a command therein to the VTR device
11
. The VTR device
11
has subdevices
13
to
15
operate, when a command is received, acceding to the concrete demand thereof. For example, when an FF (fast feed) command addressed to the VTR subdevice
13
is received, the command is delivered to the VTR subdevice
13
. The VTR subdevice
13
executes processing for controlling so as to have a mechanical system of the recording/playback system within the VTR perform FF. Further, the VTR subdevice
13
monitors various status mechamode, time code or the like of the recording/playback system, and generates a response when occasion demands. This response is transmitted to the IEEE 1394 bus transmission-reception block
12
by the VTR device
11
. The IEEE 1394 bus transmission-reception block
12
sends out the response to the bus being included in the Async communication packet.
FIG. 13
shows structures of formats of commands a
Kawamura Harumi
Sato Makoto
Shima Hisato
Frommer William S.
Frommer & Lawrence & Haug LLP
Holloway III Edwin C.
Kessler Gordon
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