Electronic printer with interleaved storage of print wheel position, hammer intensity, and carriage position data in read only memory

An impact-type electronic printer uses a rotary printing wheel and a ROM to store printing-type position data for dealing with respective printing types borne by the rotary printing wheel, hammer pressure data, and the spacing data respectively matching the designated printing types together with printing-type position data. The main CPU then draws out the printing-type position data, hammer pressure data, and the spacing data in response to the input data to allow the printer to execute the printing operation using the designated printing types in accordance with these data drawn out of the ROM, thus realizing distinctly clean printed characters. The unique system embodied by the present invention makes it possible for the controller to easily read important data from the ROM. In other words, since the control system reflecting the present invention allows the ROM to effectively store the printing-type position data, hammer pressure data, and the specifying data in two words, the control system can, for example, securely read the data merely by executing the reading operations twice.

BACKGROUND OF INVENTION 
The present invention relates to an electronic printer, e.g. an impact-type 
electronic printer using a rotary printing wheel. 
Conventional electronic printers are designed to realize a uniform printing 
depth by varying the hammer pressure for each printing type. 
Such a conventional electronic printer prints out characters and symbols 
cleanly with a uniform depth by continuously controlling the depth of the 
printed chracters according to their size. However, the conventional 
electronic printer cannot produce completely clean print merely by 
controlling the depth of the printed characters and symbols. In fact, 
cleaner printing can only be realized by adequately varying the spacing so 
that the next character is set in its printing position with reference to 
the size of the printing type. To achieve this, the controller system 
should be provided with a variety of specific spacing data for adequately 
varying the space in accordance with the magnitude of the areas of the 
respective printing type. Therefore, it is necessary to independently draw 
out from the ROM printing-type position data, hammer pressure and spacing 
data in response to the input data that represents the printable 
character. Actually, no conventional electronic printer can smoothly 
extract such data from the ROM, because it involves the entire circuitry 
in complex operations. 
SUMMARY OF THE INVENTION 
The present invention primarily aims at providing distinctly cleaner 
characters than can be printed with impact-type electronic printers using 
a rotary printing wheel. Another object of the present invention is to 
provide the impact-type electronic printer with a means for indpendently 
storing both hammer pressure data and spacing data to correctly match the 
respective printing types and such means for effectively and smoothly 
drawing out the printing-type position data, hammer pressure data, and the 
spacing data from the memory means (ROM). Briefly described, in accordance 
with the present invention, an impact-type electronic printer using a 
rotary printing wheel reflecting the preferred embodiment of the present 
invention enables the ROM to store the printing-type position data for the 
printing types borne by the rotary printing wheel, the hammer pressure 
data, and the spacing data matching the designated printing types together 
with the printing-type position data. The main CPU then draws out the 
printing-type position data, the hammer pressure data, and the spacing 
data in response to the input data to allow the printer to execute the 
printing operation using the designated printing types in accordance with 
these data drawn out of the ROM, thus realizing distinct, clean printed 
characters. 
The unique system embodied by the present invention makes it possible for 
the controller to easily read important data from ROM. In other words, 
since the control system reflecting the present invention allows the ROM 
to effectively store the printing-type position data, hammer pressure 
data, and spacing data in two words, the control system can, for example, 
read this data merely by executing the reading operation twice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a simplified block diagram of the control circuit of the 
electronic printer embodied by the present invention, as typically applied 
to typewriters. Reference number 1 indicates the 8-bit main CPU of the 
typewriter reflecting the preferred embodiment of the present invention. 
Reference numbers 2 and 3 indicate the 8-bit subordinate CPUs. Of these, 
the wheel CPU (W-CPU) 2 controls the operations of both the rotary 
printing wheel 9 and the hammer 11, whereas the carriage CPU (C-CPU) 3 
controls the operation of the carriage 14. Reference number 4 indicates 
the interface connected to external data sources which deliver the ASCII 
code to this interface 4. Reference number 5 indicates the keyboard unit 
that receives the key-code character data. Reference number 6 indicates 
the ROM which is provided with table 6A and which converts the key codes 
into the ASCII code, table 6B which stores the printing-type position data 
(WHEEL NO.) designating the physical positions of the respective printing 
types or elements (24 of FIG. 4) of the rotary printing wheel 9, hammer 
pressure data, and spacing data, while ROM 6 also contains other tables 
storing control programs. Reference number 7 indicates the RAM containing 
the input buffer 7A, the miscellaneous buffer 7B, and the sentence memory 
area 7C. 
Reference number 8 indicates the printing-wheel driver connected to the 
W-CPU 2. Reference number 9 indicates the rotary printing wheel controlled 
by the wheel driver 8. Reference number 10 indicates the hammer driver 
connected to the W-CPU 2. Reference number 11 indicates the hammer 
controlled by the hammer driver 10. Reference number 12 indicates the 
photosensor (optical rotary encoder) that detects the position of the 
rotary printing wheel 9 and delivers the data related to the position of 
this wheel to the W-CPU 2. Reference number 13 indicates the carriage 
driver connected to the C-CPU 3 and reference number 14 indicates the 
carriage controlled by the carriage driver 13. Reference number 15 
indicates the photosensor (optical rotary encoder) that detects the 
position of the carriage 14 and delivers data regarding the moving 
position of the carriage 14 to the C-CPU 3. The carriage 14 is provided 
with the rotary printing wheel 21 and the hammer 27 shown in FIG. 5. 
Referring now to FIG. 2, the composition of the printing-type position data 
(wheel number) related to the respective printing types of the rotary 
printing wheel 9, hammer pressure data, and the spacing data stored in the 
ROM 6 is described below. The rotary printing wheel 9 bears 112 printing 
types. The printing-type position data is composed of 8 bits. Although 
7-bit data composition is quite sufficient for selecting any of these 112 
printing types, the 8th bit is made available for providing data related 
to composite symbols such as $ (dollar) and -- (yen), and as a result, a 
maximum of 8 bits are made available. In the preferred embodiment of the 
present invention, the hammer pressure data and the spacing data are 
respectively composed of 4 bits to allow the control system of the printer 
to apply a maximum of 16 levels of hammer pressure and space adjustment. 
Therefore, the electronic printer incorporating the preferred embodiment 
of the present invention enables the ROM 6 to constantly store together 
the 8-bit printing-type position data, the 4-bit hammer pressure data, and 
the 4-bit spacing data. The ROM 6 is provided with 2 stages, i.e., 2 
address positions dealign with each printing type. As shown in FIG. 2 (1), 
the first stage stores the upper 4-bit contents of the 8-bit printing-type 
position data, the upper 2-bit contents of the 4-bit hammer pressure data, 
and the upper 2-bit contents of the 4-bit spacing data. On the other hand, 
the second stage in FIG. 2(2) stores 8-bit data comprised of the lower 
4-bit contents of the 8-bit printing-type position data, the lower 2-bit 
contents of the 4-bit hammer pressure data, and the lower 2-bit contents 
of the 4-bit spacing data. In addition, the ROM 6 stores the data relating 
to the 112 printing types, for example the first and second stages would 
be provided with the n-th through (224+n)th addresses. 
At least one kind of the printing-type position data, hammer pressure data, 
and the spacing data described above may be divided into one-half when the 
divided data is stored in the ROM 6. Needless to say, each element of this 
data may also be divided into any number of desired parts other than 
one-half. 
Rotary wheel electronic printers use a rotary printing wheel 21 in FIG. 4. 
The rotary printing wheel 21 has a number of spokes 22, 22--almost all 
identical in shape. Each spoke 22, 22--radially extends from the center 
hub 23 and bears a printing type 24 at its tip, forming part of the 
external circumference of the rotary printing wheel 21. Printing types 24 
include upper case and lower case characters, numerals, and a variety of 
symbols. As shown in FIG. 5, the rotary printing wheel 21 is driven by the 
rotating shaft 25a of the drive motor 25 mounted on the carriage 14 of 
FIG. 1. The drive motor 25 controls the rotation of the rotary printing 
wheel 21 so that the desired printing type 24 can be set in the correct 
printing position where the platen 26 and the hammer 27 match each other 
exactly. By causing the hammer 27 to hit the rear surface of the 
designated printing type 24 in the direction of the platen 26, the 
designated printing type 24 performs the printing and recording of the 
required data on the recording paper 28 in front of the platen 26 via an 
ink ribbon 29. 
Referring now to the operation chart of FIG. 3, the operations of the 
control system reflecting the preferred embodiment of the present 
invention are described below. First, when data designating the printable 
character is input, the main CPU 1 identifies in step 101 whether or not 
the input data belongs to the ASCII code. The input data transmitted from 
the external data sources via the interface 4 belongs to the ASCII code 
whereas the data input from the keyboard unit 5 belongs to the key code. 
When the key code is input, the main CPU 1 converts in step 102 the 
key-coded input data into the ASCII code by referring it to the conversion 
table 6A of ROM 6. As a result, all input data are standardized into the 
ASCII code. The ASCII-coded data from the interface 4 and such data 
converted into the ASCII code from the keyboard unit 5 are temporarily 
stored in the input buffer 7A of the RAM 7. The main CPU 1 then reads data 
out from the ROM 6 by addressing the positions that match the input data 
stored in the ROM 6. In this way, the printing-type position data, hammer 
pressure data, and the spacing data respectively match the ASCII code and 
can be correctly received from the table 6B of the ROM 6. As a result, the 
first-stage data shown in FIG. 2(1) (comprised of the 8-bit data 
containing the upper 4-bit contents of the printing-type position data, 
the upper 2-bit contents of the hammer pressure data, and the upper 2-bit 
contents of the spacing data) are read out of the ROM 6 in step 103 and 
then temporarily stored in the buffer 7A of the RAM 7. Next, the 
second-stage data in FIG. 2(2) (comprised of the 8-bit data containing the 
lower 4-bit contents of the printing-type position data, the lower 2-bit 
contents of the hammer pressure data, and the lower 2-bit contents of the 
spacing data) are also read out of the ROM 6 in step 104 and temporarily 
stored in the buffer 7A of the RAM 7. After the main CPU 1 has read the 
2-stage data out of the ROM 6, both the upper and lower 4-bit contents of 
the printing-type position data stored in the RAM 7 are then integrated 
into the 8-bit printing-type position data for delivery to the W-CPU 2 in 
step 105. Next, both the upper and lower 2-bit contents of the hammer 
pressure data are integrated into the 4-bit data, which is then provided 
with control data before being delivered to the W-CPU 2 in step 106. 
Likewise, the upper and lower 2-bit contents of the spacing data are 
integrated into the 4-bit spacing data, which is also provided with 
control data before eventually being delivered to the W-CPU 3 in step 107. 
The electronic printer system then proceeds to the printing operation in 
step 108. First, the main CPU 1 executes a specific operation in reference 
to the spacing data received from the C-CPU 3 and then generates the 
spacing data for providing the optimum spaces in advance of and behind the 
designated printing type. The main CPU 1 then controls the operation of 
the carriage driver 13 in response to the advance spacing data before 
activating the carriage 14 to move its position. The main CPU 1 then 
controls the operation of the printing wheel driver 8 in response to the 
printing-type position data fed from the W-CPU 2 in order that the rotary 
printing wheel 9 can precisely rotate itself up to the designated position 
where the designated printing type 24 matching the input data executes the 
printing operation. On the other hand, using the hammer pressure data 
received, the W-CPU 2 controls the operation of the hammer driver 10 to 
drive the hammer 11 at the moment when the printing type of the rotary 
printing wheel 9 matching the input data stops at the printing position so 
that the printing can be executed at the optimum pressure as determined by 
the hammer pressure data. Next, after completing the printing operation, 
by activating the hammer 27 to hit the back of the designated printing 
type 24, the C-CPU 3 then controls the operation of the carriage driver 13 
in accordance with the post-print spacing data. This causes the carriage 
14 to move its position. By applying these serial operations, the printing 
cycle for each printing type 24 is completed. The desired characters and 
symbols are thus sequentially printed and recorded by repeatedly executing 
these serial operations whenever the input data designating the desired 
characters and symbols are received. 
While only certain embodiments of the present invention have been 
described, it will be apparent to those skilled in the art that various 
changes and modifications may be made therein without departing from the 
spirit and scope of the present invention as claimed.