Printing control apparatus in page printer

In a printing control apparatus in a page printer for making prints based on print data supplied from an external unit page by page, when the page printer is in an idling state, the print data is directly converted into dot image information. When the page printer is not in the idling state, the print data is converted into descriptors while the prior page print is being formed, and the descriptors are converted into dot image information. A print is made based on the dot image information. The printing control apparatus further includes a first jam recovery block for recovering a print corresponding to a jammed paper in the page printer by using descriptors in a case where the descriptors have been stored in a page descriptor area of a memory, and a second jam recovery block for recovering a print corresponding to a jammed paper in the page printer by using dot image information which has been stored in a bit map area of the memory.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention generally relates to a printing control apparatus in 
a page printer, and more particularly to a printing control apparatus by 
which a page printer can efficiently make prints. 
(2) Description of Related Art 
A page printer makes prints page by page. The page printer has a memory 
into which dot image information for one page is mapped, and an image 
having an accurate dot layout can be printed by the page printer. Thus, in 
the page printer, high quality prints can be made at a high speed. For a 
laser beam printer, an LED printer and a liquid crystal printer, each of 
which is a page printer which can be used personally, prices are 
particularly low. 
In the page printer, the memory is provided with a plurality of bit map 
areas into each of which dot image information for one page is mapped to 
improve a printing speed. In this case, while dot image information stored 
in a bit map area is being printed out, dot image information of the next 
page is being mapped into the next bit map area by utilizing an otherwise 
idle time of a CPU. 
In the above case where the memory is provided with a plurality of bit map 
areas each of which has a capacity of one page, it is necessary for the 
memory to have a large capacity. To decrease a capacity required for the 
bit map area in the memory, the following page printer has been proposed. 
In this conventional page printer, the memory is divided into a system 
area 1, a page descriptor area 2, a working area 3 and a bit map area 4, 
as shown in FIG. 1. Information used for controlling the printer is stored 
in the system area 1. The working area 3 is used for processing various 
information such as print data supplied from a host computer. The bit map 
area 4 has a capacity of one page or between one page and two pages. That 
is, the capacity of the bit map area is less than that of two pages. Print 
data supplied from a host computer is converted into descriptors each 
having an intermediate format so that dot image information corresponding 
to the print data can be easily mapped into the bit map area 4 based on 
the descriptors. That is, a time required for converting the descriptors 
into the dot image information is less than a time required for directly 
converting the print data supplied from the host computer into the dot 
image information. The descriptors are stored in the page descriptor area 
2 in the memory. FIG. 2A indicates a bit map area 4 of one page. In a case 
where A4 sized image is printed at a rate of 240 dpi (dot per inch), the 
dot image information having 1872(width).times.2720(length) dots is mapped 
into the bit map area 4 of the memory. In this case, a bit map area 4 
having a capacity of about 640K bytes is needed. In cases of B4 image 
size, the bit map area having a capacity of about 950K bytes is needed. In 
a case of A3 image size, the bit map area 4 having a capacity of about 
1.2M bytes is needed. FIG. 2B indicates a bit map area 4 having a capacity 
between one page and two pages. In this case, the bit map area 4 is 
divided into a first area 4-1 of one page and a second area 4-2 of one 
page which are overlapped with each other so that an overlap area (O) is 
formed. In a case where the bit map has a capacity between one page and 
two pages, as shown in FIG. 2B, a printing control is carried out as 
follows. 
In step 1, dot image information corresponding to one page printing data 
supplied from the host computer is mapped into the first area 4-1 of the 
bit map area 4 starting from an origin S1. In step 2, after the dot image 
information is completely mapped into the first area 4-1, all the dot 
image information in the first area 4-1 is shifted to the second area 4-2 
of the bit map area 4 starting from an origin S2. In step 3, the dot image 
information is successively read out from the second area 4-2 of the bit 
map area 4 starting from the origin S2, and a print driving circuit is 
driven in accordance with the dot image information successively read out 
from the second area 4-2 of the bit map area 4 so that a print 
corresponding to the dot image information is formed on a recording sheet. 
While the print is being formed on the recording sheet in step 3, it is 
determined whether or not image information data in the overlap area (O) 
is finished being printed. In step 4, when it is determined that dot image 
information of the last line in the overlap area (O) is completely 
printed, since the first area 4-1 of the bit map area 4 is in an empty 
state, dot image information corresponding to the next page print data is 
mapped into the first area 4-1 starting from the origin S1. Then the above 
steps 1 through 4 are repeated a predetermined number of times 
corresponding to requested pages. 
While the dot image information in the second area 4-2 is successively read 
out and printed on the recording sheet, in step 3, the next page print 
data is converted into descriptors and the descriptors are stored in the 
page descriptor area 2 in the memory. Then, in step 4, the dot image 
information is mapped into the first area 4-1 based on the descriptors 
corresponding to the next page's print data. Thus, the dot image 
information is easily and efficiently mapped into the first area 4-1. That 
is, the prints for a plurality pages can be formed at a high speed. 
However, the above conventional process for forming prints in the page 
printer has the following disadvantages. 
Immediately after an electric power supply of the page printer is turned 
on, and immediately after the prior job for forming prints is finished, 
the bit map area 4 of the memory is empty. In this state (herein after 
referred to as an idling state), even if the bit map area 4 is empty, the 
descriptors corresponding to the first page print data must be prepared 
and stored in the page descriptor area 2. After that, the dot image 
information is prepared based on the descriptors and mapped into the bit 
map area 4. 
In this case, since immediate data such as the descriptors must be prepared 
before dot image information is mapped into the bit map area 4 although 
the bit map area 4 is empty, the mapping to form the first page is 
delayed. Particularly, in a case where the first page print data includes 
a large amount of images such as diagrams and graphs, an amount of data of 
the descriptors reaches a value in a range between few tens K bytes and 
few hundreds K bytes. That is, a large load for making the descriptors is 
applied to a processor in the page printer. As a result, it is further 
delayed to form the first page print. In addition, in a case where the 
first page print data includes many complex images, the capacity of the 
page descriptor area 2 of the memory becomes insufficient. In this case, 
since a process for converting the first page data into the descriptors is 
interrupted and the dot image information is formed directly based on the 
print data, a time for obtaining the descriptors is wasted. 
SUMMARY OF THE INVENTION 
Accordingly, a general object of the present invention is to provide a 
novel and useful printing control apparatus in a page printer in which the 
disadvantages of the aforementioned prior art are eliminated. 
A more specific object of the present invention is to provide a printing 
control apparatus in a page printer in which, immediately after the power 
supply of the page printer is turned on and immediately after the prior 
job for forming prints is finished, a time for obtaining the first page 
print can be decreased. 
The above objects of the present invention are achieved by a printing 
control apparatus in a page printer for making prints based on print data 
supplied from an external unit page by page, the apparatus comprising: 
first determination means for determining whether or not the page printer 
is in an idling state which is a state where the page printer is waiting 
for the first page print data in one print job to be supplied from the 
external unit; first control means, coupled to the first determination 
means, for controlling the page printer so that a print corresponding to 
the print data supplied from the external unit is made when the first 
determination means determines that the page printer is in the idling 
state, the first control means comprising conversion means for directly 
converting the print data supplied from the external unit into dot image 
information, so that the print is made based on the dot image information; 
and second control means, coupled to the first determination means, for 
controlling the page printer so that a print corresponding to the print 
data supplied from the external unit is made when the first determination 
means determines that the page printer is in the idling state, the second 
control means comprising first conversion means for converting the print 
data supplied from the external unit into descriptors while a prior print 
is being made by the page printer, the descriptors being intermediate 
information used for converting the print data to dot image information, 
and second conversion means for converting the descriptors obtained by the 
first conversion means into dot image information, so that the print is 
made based on the dot image information. 
According to the present invention, when the page printer is in the idling 
state, the print data supplied from the external unit (e.g. the host 
computer) is directly converted into the dot image information, and when 
the page printer is not in the idling state, the print data is converted 
into the descriptors while the prior page print is being formed. Thus, 
prints can be efficiently made in the page printer. 
Another object of the present invention is to provide a printing control 
apparatus in a page printer in which prints formed on jammed papers in the 
page printer can be efficiently recovered. 
The above objects of the present invention are achieved by a printing 
control apparatus further comprising first jam recovery means for 
recovering a print corresponding to a jammed paper in the page printer by 
using descriptors in a case where the descriptors have been stored in the 
page descriptor area of the memory; and second jam recovery means for 
recovering a print corresponding to a jammed paper in the page printer by 
using dot image information which has been stored in the bit map area of 
the memory. 
The above objects of the present invention are also achieved by a print 
control apparatus further comprising data save means for saving the print 
data in a saving area provided with the memory when the first control 
means is activated; and third jam recovery means for recovering a printout 
corresponding to a jammed paper in the page printer by using the print 
data saved in the saving area in the memory. 
According to the present invention, various data such as the descriptors 
and the print data can be used for recovering a printout corresponding to 
a jammed paper. Thus, the printout corresponding to the jammed paper can 
be efficiently recovered. 
Additional objects, features and advantages of the present invention will 
become apparent from the following detailed description when read in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A description will now be given of an embodiment of the present invention. 
Referring to FIG. 3, which shows a basic structure of a page printer, a 
host computer 10 is coupled to a controller 12 of a page printer so that 
print data edited in the host computer 10 is supplied to the controller 
12. A memory 14 utilized by the controller 12, a print engine 16 for 
driving a mechanism for forming prints, a paper feed mechanism 18 for 
feeding recording papers on which prints should be formed, and a jam 
sensor 20 for detecting a paper jam occurring in the paper feed mechanism 
18 are connected to the controller 12. The memory 14 has the system area 
1, the page descriptor area 2, the wording area 3 and the bit map area 4, 
as shown in FIG. 1. The bit map area 4 has a capacity for one page or 
between one page and two pages, as shown in FIG. 2A or 2B. Each of the 
other areas 1, 2 and 3 has a predetermined capacity. A page descriptor 
formed of descriptors for each page print data is written in the page 
descriptor area 2. Thus, page descriptors stored in the page descriptor 
area 2 for the first page, the second page, the third page, . . . 
respectively correspond to printed pages of the first page, the second 
page, the third page . . . , as shown in FIG. 4A. Each of the descriptors 
representing a font of a character has a format shown in FIG. 4B. That is, 
a descriptor has information indicated by FUNC, FLAG and LINK. FUNC is 
information representing a function (a subroutine offset) used for laying 
out dot image information corresponding to a character identified by the 
descriptor in the bit map area 4. FLAG is information representing a mode 
of a process for writing the dot image information in the bit map area 4. 
LINK is link information (an offset) of the descriptor. The descriptor for 
a character further has information representing a font size (W and H), 
coordinate data (X and Y) of a position at which the font should be mapped 
into the bit map area 4, and a font raster image address. The font size is 
defined by a width (W) and a height (H), as shown in FIG. 4D. Each of the 
descriptors representing an image has a format shown in FIG. 4C. That is, 
a descriptor has information indicated by FUNC, FLAG and LINK, coordinate 
data (X and Y) of a position at which the image should be mapped into the 
bit map area 4 in the same manner as that for a font of a character. The 
descriptor for an image further has information regarding an offset of an 
image save area. 
Descriptors in the same page descriptor are linked by the link information 
(LINK). Thus, all the descriptors in the same page descriptor are selected 
with reference to the link information (LINK), and dot image information 
corresponding to the selected descriptors is mapped into the bit map area 
4. In an idle time of a processor (CPU) of the controller 12, page 
descriptors are written in the page descriptor area 2 of the memory 14 
until the page descriptor area 2 is filled with the descriptors. 
Print data supplied from the host computer 10 to the page printer is 
processed in accordance with the flow charts shown in FIGS. 5A through 7. 
The process shown in FIGS. 5A through 7 is carried out by the controller 
12 
Referring to FIG. 5A, step 101 determines whether or not print data 
supplied from the host computer 10 is in a receiving buffer in the 
controller 12. When the print data is stored in the receiving buffer, step 
102 determines whether or not the page printer is in an idling state. The 
idling state is defined as a state in which the page printer is waiting 
for a print start instruction immediately after the power supply of the 
page printer is turned on or immediately after the prior job for forming 
prints is finished. When step 102 determines that the page printer is in 
the idling state, the process proceeds to step 301 shown in FIG. 5C. 
At this time, information regarding conditions, such as a printing pitch 
and various printing modes, required for forming a printout for one page 
has already been transmitted from the host computer 10 along with the 
print data and stored in the receiving buffer. In step 301, the above 
information regarding the conditions required for forming a print for one 
page is saved in the working area 3 of the memory 14. Then step 302 sets a 
third jam recovery mode (3) in the controller 12. The third recovery made 
(3) will be described later. After this, step 303 determines whether or 
not the print data is in the receiving buffer. In a case where the print 
data is in the receiving buffer, a process for saving the print data for a 
paper jam occurring in the paper feed mechanism 18 is carried out in 
accordance with the following steps. Step 304 determines whether or not a 
saving area provided in the working area 3 of the memory 14 is filled with 
print data. When a result obtained in the step 304 is NO, step 305 
determines whether or not a recovery mode flag is set. In a case where the 
recovery mode flag is not set, step 306 determines whether or not a second 
jam recovery mode (2) is set. When step 306 determines that the second jam 
recovery mode is not set, step 307 saves the print data stored in the 
receiving buffer in the saving area. 
After the print data is saved in the saving area as described above, the 
print data stored in the receiving buffer is processed and converted into 
dot image information, in step 308. Then, step 309 carries out a drawing 
process for mapping the dot image information in the bit map area 4. Then, 
step 310 determines whether o not dot image information for one page is 
mapped into the bit map area 4, and the above steps 303-310 are repeated 
until the dot image information for one page is completely mapped into the 
bit map area 4. 
In the above process, when step 304 determines that the saving area is 
filled with the print data, step 311 releases the saving area so that 
saving of the print data is interrupted, and step 312 sets a second jam 
recovery mode (2). Then the process proceeds to step 308. In this case, as 
the print data includes a large amount of image information, the saving 
area cannot store all the print data. Thus, the print data is converted 
into the dot image information, and the dot image information is stored in 
the bit map area 4 of the memory 14. Then the dot image information is 
being saved in the bit map area 4 until a printout corresponding to the 
dot image information is completely formed without a paper jam. 
In addition, when the result obtained by either step 305 or step 306 is 
YES, the process proceeds directly to step 308. 
When the dot image information for one page is completely mapped into the 
bit map area 4, the process proceeds to step 201 shown in FIG. 5B. 
Step 201 determines whether or not the print engine 16 is in a ready state. 
In a case where the print engine 16 is in the ready state, the print 
engine 16 is driven in step 202, so that a print starts to be formed. The 
print is then formed on a sheet of recording paper fed by the paper feed 
mechanism 18 by using the dot image information mapped into the bit map 
area 4 of the memory 14. 
While the print of the first page is being formed by the page printer, the 
process is carried out from the step 101 shown in FIG. 5A again. In this 
case, after step 101 determines that the print data for the next page 
supplied from the host computer 10 is stored in the receiving buffer, step 
102 determines that the page printer is not in the idling state. Then, 
step 103 sets a first jam recovery mode (1). After this, step 104 
determines whether or not the print data is stored in the receiving 
buffer. When step 104 determines that the print data is stored in the 
receiving area, step 105 converts the print data stored in the receiving 
area into descriptors as shown in FIGS. 4b and 4C. The descriptors 
obtained in step 106 are stored in the page descriptor area 2 of the 
memory 14. Then step 106 determines whether or not the descriptors 
corresponding to the print data for one page is stored in the page 
descriptor area 2, and the above steps 104, 105 and 106 are successively 
repeated until the descriptors corresponding to the print data for one 
page are completely stored in the page descriptor area 2. While the above 
steps 104, 105 and 106 are successively repeated, step 109 determines 
whether or not the page descriptors is filled with descriptors. When the 
descriptors corresponding to the print data for one page are completely 
stored in the page descriptor area 2 (the result of step 106 is YES), step 
107 determines whether or not the bit map area 4 is empty. Here, when the 
print of the first page (the prior page) is finished, the bit map area 4 
becomes empty. At this time, step 107 determines that the bit map area 4 
is empty. Thus, the process proceeds to step 108, and step 108 carries out 
the drawing process for mapping dot image information in the bit map area 
4 based on the descriptors stored in the page descriptor area 2. After 
this, the process is carried out in accordance with a flow chart shown in 
FIG. 5B, so that the next page is printed. 
While the print data is being converted into the descriptors (steps 104, 
105 and 106), the page descriptor area 2 is filled with the descriptors, 
the process proceeds from step 109 to step 401 shown in FIG. 5D. 
Referring to FIG. 5D, step 401 determines whether or not the bit map area 4 
is empty. When the printing of the prior page is finished, the bit map 
area 4 becomes empty. At this time, the process proceeds to step 402. Step 
402 carries out the drawing process for mapping dot image information in 
the bit map area 4 based on the descriptors into which the print data has 
been already converted. After this, step 403 determines whether or not the 
print data which is not converted into the descriptors is stored in the 
receiving buffer. When the result obtained in step 403 is YES, the print 
data which is not converted into the descriptors is processed and 
converted into the dot image information, in step 404. Then step 405 
carries out the drawing process for mapping the dot image information in 
the bit map area 4. Step 406 determines whether of not the dot image 
information for one page is completely mapped into the bit map area 4. The 
above steps 403, 404, 405 and 406 are successively repeated until the dot 
image information for one page is completely mapped into the bit map area 
4. When step 406 determines that the dot image information for one page is 
completely mapped into the bit map area 4, step 407 sets the second jam 
recovery mode (2). After this, the process is carried out in accordance 
with the flow chart shown in FIG. 5B, so that the print of the next page 
is formed. 
While the process is being carried out in accordance with the flow charts 
shown in FIGS. 5A-5D, controller 12 carries out an interrupt process for 
detecting a paper jam based on a detecting signal supplied from the jam 
sensor 20 as shown in FIG. 6. Referring to FIG. 6, after the interrupt 
process starts in step 500, when step 501 determines that a paper jam 
occurs, step 502 sets a paper jam flag. 
In the above process shown in FIGS. 5A-5D, a plurality of checking steps 
for checking whether or not a paper jam occurs are carried out. A first 
checking step C1, a second checking step C2 and a third checking step C3 
are respectively carried out with steps 101, 104 and 107, as shown in FIG. 
5A. A fourth checking step C4 is carried out with step 201 as shown in 
FIG. 5B. A fifth checking step C5 and a sixth checking step C6 are 
respectively carried out with steps 401 and 403, as shown in FIG. 5D. Each 
of the checking steps C1-C6 is carried out in accordance with a flow chart 
shown in FIG. 7. 
Referring to FIG. 7, step 601 determines whether or not the paper jam flag 
is set. When the result obtained in step 601 is NO, the process returns to 
a predetermined step shown in FIGS. 5A-5D. When a paper jam has been 
detected by the interrupt process shown in FIG. 6, the result obtained in 
step 601 is YES. In this case, after an instruction for releasing a state 
where the paper jam flag is set is recognized by the controller 12 (in 
step 602), step 603 clears the paper jam flag. After that, step 604 
determines what type of jam recovery mode is set. 
When step 604 determines that the first jam recovery mode (1) is set, the 
process is carried out in accordance with steps 611, 612 and 613. Step 611 
returns a pointer to a lead address of the descriptors corresponding to a 
jammed paper which descriptors have been stored in the page descriptor 
area 2 of the memory 14. Step 612 resets a program counter to a value 
corresponding to an address of a returning point (A) shown in FIG. 5A. 
Then step 613 rewrites data in a stack area provided in the system area 1 
so that the process can start from the returning point (A). After the 
steps 611, 612 and 613 are completed, the process starts from the 
returning point (A). That is, the dot image information is prepared based 
on the descriptors corresponding to the jammed paper, and mapped into the 
bit map area 4. The process is carried out in accordance with the flow 
chart shown in FIG. 5B, so that a print is then formed on a new sheet of 
recording paper fed by the paper feed mechanism 18 by using the dot image 
information mapped into the bit map area 4 of the memory 14. That is, the 
print which was formed on the jammed paper is recovered. 
When step 604 determines that the second jam recovery mode (2) is set, the 
process is carried out in accordance with steps 621 and 622. Step 612 
resets the program counter to a value corresponding to an address of a 
returning point (B) shown in FIG. 5B. Then step 622 rewrites data in the 
stack area so that the process can start from the returning point (B). 
After the steps 621 and 622 are completed, the process starts from the 
returning point (B). That is, the process is carried out in accordance 
with the flow chart shown in FIG. 5B. In this case, dot image information 
corresponding to the jammed paper has been already mapped in the bit map 
area 4 of the memory 14. Thus, a printout is formed on a new recording 
paper fed by the paper feed mechanism 18 by using the dot image 
information mapped into the bit map area 4 of the memory 14. That is, the 
printout which was formed on the jammed paper is recovered. 
When step 604 determines that the third jam recovery mode (3) is set, the 
process is carried out in accordance with steps 631, 632, 633, 634 and 
635. Step 631 loads information regarding the conditions required for a 
print corresponding to the jammed paper in a predetermined area in the 
working area 3 of the memory 14. Step 632 sets the recovery mode flag, and 
then step 633 changes a read pointer of the receiving buffer to the lead 
address of the saving area provided in the working area 3. Step 364 resets 
the program counter to a value corresponding to an address of a returning 
point (C) shown in FIG. 5C. Then step 635 rewrites data in the stack area 
so that the process can start from the returning point (C). After the 
steps 631, 632, 633, 634 and 635 are completed, the process starts from 
the returning point (C). That is, the process is carried out in accordance 
with the flow chart shown in FIG. 5C. In this case, the print data 
corresponding to the jammed paper has been stored in the saving area 
provided in the working area 3 of the memory 14. Thus, after it is 
determined that the recovery mode flag is set in step 305, the print data 
stored in the saving area is converted into the dot image information. The 
dot image information is mapped into the bit map area 4 of the memory 14 
(steps 308, 309 and 310) As a result, a printout is formed on a new 
recording paper fed by the paper feed mechanism 18 by using the dot image 
information mapped into the bit map area 4 of the memory 14. That is, the 
print which was formed on the jammed paper is recovered. 
According to the above embodiment, in a case where the page printer is in 
the idling state, descriptors corresponding to print data are not made, 
and the print data is directly converted into dot image information. In a 
case where the page printer is not in the idling state, the print data is 
converted into descriptors while a printout for the prior page is being 
formed. After this, dot image information is mapped in the bit map area 4 
based on the descriptors. Thus, printouts are successively formed 
efficiently. 
In addition, in a case where the descriptors has been stored in the page 
descriptor area 2, a print corresponding to a jammed paper is recovered by 
using the descriptors stored in the page descriptor area 2. In a case 
where the print data has been saved in the saving area, a printout 
corresponding to a jammed paper is recovered by using the print data 
stored in the saving area. Further, in a case where print data includes a 
large amount of image information, the print data for one page and the 
descriptors for one page cannot be respectively stored in the saving area 
and the page descriptor area 2. In this case, the dot image information 
formed from the descriptors and the print data is saved in the bit map 
memory. Then a print corresponding to a jammed paper is recovered by using 
the dot image information stored in the bit map area 4. Thus, the jam 
recovery process can be efficiently carried out. 
The present invention is not limited to the aforementioned embodiments, and 
variations and modifications may be made without departing from the scope 
of the claimed invention.