Facsimile and static presentation processing – Static presentation processing – Communication
Reexamination Certificate
1999-10-12
2003-09-09
Coles, Edward (Department: 2722)
Facsimile and static presentation processing
Static presentation processing
Communication
C358S001900, C358S001160, C358S001130, C358S473000, C358S001120
Reexamination Certificate
active
06618164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a network printer which performs printing on the basis of data received via a network such as a LAN (Local Area Network), and also to a network printing method.
The present application is based on Japanese Patent Application No. Hei. 10-291910, which is incorporated herein by reference.
2. Description of the Related Art
In a printer which is locally connected to a host computer via a parallel I/F or the like, print data are input basically as it is, and at a relatively constant rate. In such a local printer, therefore, it is requested to store received print data as they are into a reception buffer, and printing can be enabled by only sequentially taking out stored data and interpreting the data.
Recently, however, a network printer which is to be connected to a host computer via a network such as a LAN is widely used. In such a network, usually, data communication between the host computer and the printer is performed by using a protocol hierarchy in which plural protocols are layered. When print data are transmitted from the host computer, therefore, the print data are divided into packets of a variable or fixed length, and data other than the print data, such as a destination address, a source address, the data length, and a frame check are added to each packet. In the printer, extra data such as the destination address are removed away from the received packet while tracing back through the protocol hierarchy, and the original print data are then reconstructed.
In this way, in the case of a network printer, print data must be stored into a reception buffer after the data are reconstructed from a packet. Therefore, a network printer is provided with a dedicated CPU (Central Processing Unit) or MPU (Micro Processing unit), in addition to that for producing a print image.
In a network printer described above, the packet reception from a network and production of a print image are processed by different CPUs, respectively. The CPU for a communication process is used only for a network process, and the CPU for print image production is used for producing a print image (producing a print request), thereby producing problems in that the utilization ratios of the CPUs are low, and that the production cost is increased. When complex bidirectional communications are to be performed between the network printer and the host computer, a protocol for coupling the CPU for a communication process with the CPU for print image production is additionally required. Furthermore, data are transmitted between the CPUs, so that the number of operations of copying data between memories tends to be increased, thereby producing another problem in that the process efficiency is low.
In order to solve such problems, it is contemplated that a CPU of relatively high performance executes both a communication process (communication task) and an image production process (image production task). In this case, however, the use of the single CPU causes the process efficiency to be instead lowered unless executions of the tasks are suitably distributed. In the case where the operation state of the communication task continues for a long term, the packet reception from a network can be rapidly processed, but the operation state of the image production task is lowered, so that a long time period elapses before starting the actual printing, whereby the throughput of printing is lowered. In contrast, when the operation state of the image production task is enhanced, the packet reception is delayed and a long time period elapses before the host computer is released from the transmission of print data. Switching between tasks requires a time period of about several hundreds of microseconds. When the tasks are frequently switched over, therefore, waste switching periods are accumulated. As a result, there arises a fear that the process efficiency is lowered.
SUMMARY OF THE INVENTION
The invention has been conducted in view of various problems discussed above. It is an object of the invention to provide a network printer and a network printing method in which the operation states of reception of data from a network and image data production in a printer can be suitably controlled. It is another object of the invention to provide a network printer and a network printing method in which the execution privilege of a processing unit which is to be allocated to a communication process and an image production process is suitably controlled, thereby enabling both the processes to be efficiently executed.
In order to attain the objects, in the network printer of the invention, a communication process and an image production process are controlled in accordance with a rate of receiving data from a network and a data processing rate in a printer.
According to a first aspect of the invention, a network printer which performs printing on the basis of data received via a network is provided. The printer comprises: a communication processing section which receives data via a network; an image production processing section which interprets the data supplied from the communication processing section, and produces image data; a print processing section which controls a drive of a print engine on the basis of the image data supplied from the image production processing section, thereby performing printing; and an operation state controlling section which, in accordance with a rate of receiving data from the network and a data processing rate in the image production processing section, controls an operation state of the communication processing section and an operation state of the image production processing section.
Data (packet) which are transmitted from a host computer to a network such as a LAN are received by the communication processing section. Based on a protocol hierarchy and the like, the communication processing section configures print data from the received data. The image production processing section interprets the data supplied from the communication processing section, and produces image data. The print processing section controls the drive of the print engine on the basis of the image data, thereby performing printing.
The communication processing section and the image production processing section use computer resources such as a memory and a CPU. Typically, at least the communication processing section and the image production processing section can be executed by a single processing unit. When one of the processing sections occupies the computer resources for a long term, therefore, the execution of the other processing section is hindered. When the execution time period of the communication processing section is long, for example, the data reception from the network can be smoothly performed, but the image production process is delayed. In contrast, when the execution time period of the image production processing section is prolonged, the data reception from the network is delayed.
For example, it may be contemplated that executions of the processing sections are switched over at predetermined periods or at each time when a given amount of data have been received. The suitable execution time period of the communication processing section is affected by the rate of receiving data from the network, and that of the image production processing section is affected by the data processing rate of the image production process. The data receiving rate and the data processing rate are varied every moment in accordance with the situations. Namely, when the network is busy, the timing of a packet arrival from the network is unstable and the data processing rate is lowered. Even when the communication processing section is provided with the execution privilege of the CPU for a long term during a period when the network is busy, the substantial operation time period is short. Therefore, the computer resources are wastefully occupied, and a waste waiting time of the image production processing section is prolonged. In contrast, when the tra
Coles Edward
Ebrahimi Saeid
Seiko Epson Corporation
Sughrue & Mion, PLLC
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