Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-08-25
2002-11-26
Wallerson, Mark (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S515000, C358S523000
Reexamination Certificate
active
06486972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video data transfer apparatus, and, more particularly, to a video data transfer apparatus suitable for transferring video data to a printer engine from a frame memory.
2. Description of the Related Art
One conventional tandem type color printer is equipped with four independent video transfer circuits respectively associated with video data of yellow, magenta, cyan and black. In this printer, the individual video transfer circuits transfer video data to a printer engine from a frame memory.
FIG. 13
is a block diagram showing the schematic structure of a video transfer section of the conventional tandem type color printer. In the structure illustrated in
FIG. 13
, one frame of video data of yellow (Y), magenta (M), cyan (C) and black (K) are stored in a DRAM
101
. The yellow video data is transferred to a color printer engine
106
by a DMAC (Dynamic Memory Access Controller)
102
for yellow (hereinafter called Y-DMAC
102
). The magenta video data is transferred to the color printer engine
106
by a DMAC
103
for magenta (hereinafter called M-DMAC
103
). The cyan video data is transferred to the color printer engine
106
by a DMAC
104
for cyan (hereinafter called C-DMAC
104
). The black video data is transferred to the color printer engine
106
by a DMAC
105
for black (hereinafter called K-DMAC
105
).
In a case of implementing fast video data transfer to permit a tandem type color printer having this structure and a resolution of, for example, 300 dpi to operate in burst mode (the operation mode to output four consecutive addresses in a single access), each of the Y-DMAC
102
, the M-DMAC
103
, the C-DMAC
104
and the K-DMAC
105
requires a data capacity of 32-bit latch×4 (quantity)×2 (lines).
If this scheme is applied to a high-resolution tandem type color printer with a resolution of, for example, 600 dpi, each of the Y-DMAC
102
, the M-DMAC
103
, the C-DMAC
104
and the K-DMAC
105
requires a data capacity of 64-bit latch×4 (quantity)×2 (lines). Therefore, the total capacity of the whole DMACs is 64-bit latch×4 (quantity)×2 (lines)×4 (colors) or 2048 bits.
The conventional tandem type color printer, as apparent from the above, requires that the capacity of each of the Y-DMAC
102
, the M-DMAC
103
, the C-DMAC
104
and the K-DMAC
105
should be increased in order to transfer video data fast to the color printer engine
106
from the DRAM
101
or adapt this printer to a high-resolution printer. This suffers an increase in the circuit scale.
If video data stored in the DRAM
101
has been compressed in advance, an expander or a decompressor should be provided at the previous stage of each of the Y-DMAC
102
, the M-DMAC
103
, the C-DMAC
104
and the K-DMAC
105
. In this case, the circuit scale becomes larger.
A variation in the operation speeds of the Y-DMAC
102
, the M-DMAC
103
, the C-DMAC
104
and the K-DMAC
105
, if any, results in an overrun error in which before the slowest one of the four DMACs completes the necessary operation, the other DMACs start the next operations.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a video data transfer apparatus capable of transferring video data fast while suppressing an increase in the circuit scale.
To achieve the above object, according to a first aspect of this invention, there is provided a video data transfer apparatus comprising:
a frame memory where plural pieces of video data representing images of different colors;
a video buffer for storing every predetermined amount of video data supplied thereto;
read control means for accessing the video buffer to read video data stored in the frame memory and representing images of individual colors, color by color, and supplying the read video data to the video buffer; and
a plurality of video transfer means for accessing the video buffer and transferring those of the video data stored in the video buffer which represent images of different colors to a printer engine.
This structure can allow a plurality of video transfer means to share a single video buffer and make it unnecessary to provide a video buffer for each video transfer means. The use of a fast-readable video buffer therefore accomplishes fast transfer of video data to the printer engine while suppressing an increase in the circuit scale. If the frame memory is constituted by a DRAM, the use of, for example, an SRAM for the video buffer implements fast reading of video data.
According to a second aspect of this invention, there is provided a video data transfer apparatus for sequentially transferring each piece of video data representing each color component of an image having a plurality of colors to a printer engine for sequentially generating a transfer request for the each piece of video data and sequentially acquiring the each piece of video data supplied thereto, which apparatus comprises:
a frame memory for storing the each piece of video data representing the each color component;
a video buffer for storing every predetermined amount of video data supplied thereto;
video transfer means for accessing the video buffer and transferring the video data stored in the video buffer to the printer engine in a supply order of the video data to the video buffer, in response to the transfer request generated by the printer engine; and
read control means for sequentially reading the video data, stored in the frame memory and representing images of individual colors, color by color, and accessing the video buffer to sequentially supply the read video data to the video buffer.
This structure can allow a plurality of video transfer means to share a single video buffer and make it unnecessary to provide a video buffer for each video transfer means. The use of a fast-readable video buffer therefore permits video data to be sequentially transferred fast to the printer engine while suppressing an increase in the circuit scale.
According to a third aspect of this invention, there is provided a video data transfer apparatus for transferring video data representing an image to a printer engine from a frame memory having an area for storing the video data, which apparatus comprises:
read address generation means for generating a read address for designating that of areas in the frame memory from which the video data is to be read out;
a video buffer having an area for storing a predetermined amount of video data;
write counter means for generating a write address for designating that of areas in the video buffer in which the video data is to be written;
write control means for, when generating an access request to the video buffer and access permission is granted, reading video data from the area in the frame memory indicated by the read address and writing the read video data in the area in the video buffer indicated by the write address;
read control means for, when generating an access request to the video buffer and access permission is granted, reading the video data from the video buffer;
read end signal generation means for generating a read end signal in response to reading of the predetermined amount of video data from the video buffer by the read control mans;
transfer means for transferring the video data read by the read control means to the printer engine;
write instruction means for generating an instruction to write next video data in the video buffer with respect to the write control means based on the read end signal; and
access control means for granting access permission to one of the write control means and the read control means which have generated the access requests to the video buffer,
the write control means having means generating the access request to the video buffer in response to the instruction generated by the write instruction means.
This structure can permit a plurality of read control means to share a single video buffer, thus making it possible to reduce the circuit scale needed to transfer data to
Casio Computer Co. Ltd.
Frishauf Holtz Goodman & Chick P.C.
Wallerson Mark
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