Facsimile and static presentation processing – Static presentation processing – Memory
Reexamination Certificate
1999-09-29
2003-12-16
Coles, Edward (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Memory
C358S001160, C358S001150, C358S001200
Reexamination Certificate
active
06665088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a page printer used with a computer system, etc., and in particular to control of the operation of storing image data in buffer memory, reading the image data from the buffer memory, and transferring the image data to a print engine.
The present application is based on Japanese Patent Applications No. Hei. 10-275074 and No. Hei. 11-97997, which are incorporated herein by reference.
2. Description of the Related Art
In a page printer, it is a general rule that the speed at which image data is expanded into a bit map and written into buffer memory differs from the speed at which image data is read from the buffer memory and is transferred to a print engine. Often, buffer memory has a small capacity and cannot store one page of image data. Thus, particularly for a complicated image of a large amount of data, image data expansion and write into the buffer memory is too late for the transfer timing to the print engine and an error in which data to be read from the buffer memory runs out during printing the page and the printing cannot be continued may occur (the error is referred to as an underrun error in the specification). In contrast, image data expansion and write into the buffer memory is too fast and the buffer memory becomes full, then an error in which the subsequent data cannot be written may occur (the error is referred to as an overrun error in the specification).
To solve this problem, in a page printer in Japanese Patent No. 2663861, a match between the buffer memory write address and read address is detected, whereby error occurrence is detected and the host is informed of the error occurrence, then informs the user of the error occurrence so that the user can take proper steps.
However, the advantage of the related art described above is only to inform the user of error occurrence when an error occurs for taking proper steps. For the user, it is ideal that no error occurs and print always succeeds. It is more desirable that if an error occurs, the system automatically takes proper steps for handling the error.
SUMMARY OF THE INVENTION
It is an object of the invention to prevent an overrun error from occurring.
It is another object of the invention to prevent an underrun error from occurring.
It is still another object of the invention to automatically take proper steps and retry printing, thereby causing the retried printing to succeed if an underrun error occurs.
According to a first aspect of the invention, there is provided a page printer comprising memory containing a buffer, an image output section for forming an image based on data and outputting the image, a reception section for writing data received from a host into the buffer, a transfer section for transferring the data in the buffer to the image output section, and a control section for controlling the reception section and the transfer section. The control section permits the transfer section to transfer the data in the buffer after at least a part as much as a predetermined amount P, of one page of data from the host is stored in the buffer. The predetermined amount P is equal to or less than the size of the buffer and is set so that the predicted point in time at which the transfer section will complete transferring of all of one page of data from the buffer becomes later than the predicted point in time at which the reception section will complete writing of all of the page of data into the buffer.
According to the page printer, the transfer start timing is controlled so that write of received data into the buffer always precedes transfer of the data from the buffer in the process of reception and transfer of one page of data, thus an underrun error is prevented.
Preferably, just before reception of each page is started, the predetermined amount P is determined so as to substantially satisfy the relation
M≧P>T
(&agr;−(
x/y
))
where x is predicted data reception speed from the host, y is predicted data transfer speed to the image output section, &agr; is a predicted compression rate of data from the host, T is the total number of data pieces of one page, and M is the buffer size.
Preferably, the predetermined amount P is determined by the printer itself. Preferably, the host determines the predetermined amount P and specifies the amount for the printer. When the host determines the predetermined amount P, the predetermined amount P is easy to set appropriately because generally the CPU of the host is high performance.
Preferably, if the buffer has an available capacity reduced to a predetermined minimum amount even before data as much as the predetermined amount P is stored in the buffer, the printer spontaneously starts transferring the data in the buffer, whereby if the predetermined amount P is not appropriate, an event in which the buffer becomes full is avoided.
According to a second aspect of the invention, there is provided a page printer comprising memory containing a buffer, an image output section for forming an image based on data and outputting the image, a reception section for writing data received from a host into the buffer, a transfer section for transferring the data in the buffer to the image output section, and a control section for controlling the reception section and the transfer section. The control section permits the transfer section to transfer the data in the buffer at a predetermined start timing. The start timing is set variably in response to a parameter affecting an increase or decrease in the data in the buffer. For example, the parameters affecting an increase or decrease in the data in the buffer are predicted data reception speed from the host, predicted data transfer speed to the image output section, a predicted compression rate of data from the host, the total number of data pieces of one page, the buffer size, etc. The start timing can be set in response to at least one of the parameters. Alternatively, the start timing can be set in response to different information substantially corresponding to the predicted data reception speed from the host, for example, the communication port, communication mode, etc., used with communication between the host and the printer.
According to the page printer, appropriate start timing such that no underrun error occurs and that the buffer does not become full, for example, for each page can be set, for example, for each page.
Preferably, the start timing is applied when at least a part as much as a predetermined amount P, of one page of data from the host is stored in the buffer, and the predetermined amount P is set so as to substantially satisfy
M≧P>T
(&agr;−(
x/y
))
where x is predicted data reception speed from the host, y is predicted data transfer speed to the image output section, &agr; is a predicted compression rate of data from the host, T is the total number of data pieces of one page, and M is the buffer size.
According to a third aspect of the invention, there is provided a page printer comprising memory containing a buffer; an image output section for forming an image based on data and outputting the image, a reception section for writing data received from a host into the buffer, a transfer section for transferring the data in the buffer to the image output section, an error detection section for detecting an underrun error caused by the fact that a read address of the transfer section from the buffer catches up with a write address of the reception section into the buffer, and an error notification section for notifying the host of occurrence of the underrun error. When the host is notified of underrun error occurrence from the page printer, it resends the data to the page printer under a condition where the underrun error is harder to occur.
When the underrun error occurs, the data is automatically resent under a condition where the underrun error is harder to occur (the process is repeated stepwise depending on the situation), whereby retry printing can be made to succeed as the data is resent without caus
Chiba Noriyoshi
Chihara Kazunori
Maruyama Michio
Murata Sunao
Ogata Hiroyasu
Coles Edward
Lamb Twyler
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