JP3064718B2 - Serial printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing control system for high-density printing of a serial printer.

[0002]

2. Description of the Related Art A serial printer for printing a character or a bit image in a dot matrix is widely used because of its excellent cost performance.
In many serial printers, the print head is composed of a wire or a heating resistor, and is driven by setting a drive voltage according to the supplied power in a normal printing state. However, if there is an area with high print density in one print line, the drive voltage will decrease. Especially in the case of a head using a wire, the impact force will decrease. In severe cases, the drive frequency cannot be followed and dot dropout will occur. There was a problem in printing quality such as a problem.

In order to avoid this, Japanese Patent Application Laid-Open No. 2-3334 discloses printing duty data for each print line in order to determine whether or not high-density printing is performed. High-density printing is determined based on the ratio of the duty numbers. In the case of high-density printing, a print head protection operation such as division printing is performed.

In Japanese Patent Application Laid-Open No. 2-57374, duty calculation is performed by adding all print bits in a one-line print buffer for one line by a high duty detection circuit (the number of print bits / the total number of bits in the print buffer). Do
When the duty becomes high, the printing speed is reduced to perform printing.

[0005]

However, in any of the conventional examples, the calculation of the duty for high-density printing detection is performed in units of one printing line. There was a disadvantage that it could not be handled.
Further, since it is necessary to calculate the duty data of the character data of one print line as a detection means for high density printing, an addition circuit for each character data and a division circuit after all addition processing are required, and the circuit configuration becomes complicated. There was also a drawback.
Further, since the processing time required for high-density printing detection due to the addition and division operation processing becomes longer, there is another disadvantage that the printing processing time of the entire printer becomes longer and the printing speed decreases.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a serial printer which can cope with local high-density printing.

[0007]

SUMMARY OF THE INVENTION A serial printer according to the present invention is a serial type printer which performs printing with a head constituted by a wire or a heating resistor.
When printing characters using character codes transmitted from an external device, the printing speed for each character code corresponding to the control code that sets the print mode is stored in memory, and printed before the start of printing one print line. The printing speed for each character code is determined by speed determining means, and printing of one line is performed at the determined minimum printing speed in one printing line.

[0008]

According to the serial printer of the present invention, the printing speed of one print line corresponding to the local high density can be set with a simple circuit configuration, and the voltage drop of the head drive power supply circuit is small even in the high density printing. That is, printing is performed while ensuring the driving voltage of the head.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described according to one embodiment. FIG. 6 shows an external view of the serial impact printer of the embodiment. 20 is a head, 21 is printing paper, 22 is a platen,
25 is a carriage. The head 20 is a carriage 25
And connected to the motor 23 by a connecting member such as a timing belt 24, and the carriage 25 is driven by the motor.
Is printed according to the movement of.

FIG. 4 shows a character code table of characters to be printed. One byte character code corresponds to each character,
FIG. 4 shows the character codes in hexadecimal. COD
The row of E is the upper nibble, and the column is the lower nibble. For example, the character "A" is represented by a character code 41H (H means a hexadecimal number). Character code 00H to 1F
H is a code used for controlling the printer and is not a character to be printed. The characters to be printed have different printing densities as can be understood from the character configuration, and have various densities from low-density characters such as "!" (Character code 21H) to high-density patterns of character codes DBH.

In the character code table, a code table corresponding to each language other than the example of FIG. 4 is provided, and the language is selected and printed by a control command of the printer. The present invention relates to a control method for printing characters such as character codes B1H, B2H, DBH to DDH in FIG. 4, which are high-density characters among these characters.

FIG. 1 shows a circuit block diagram of the present invention. 1
Is a CPU that controls the entire printer, and 2 is a ROM (Read) that stores a control program and character data.
Only Memory). The CPU 1 performs printing by controlling the head drive circuit 8, the carriage drive circuit 3, and the paper feed motor drive circuit 4 according to a command from the external device 9. The command from the external device 9 is temporarily stored in the input data buffer 5.
The CPU 1 sequentially determines the input data and controls the printer.

Since the print character data in the input data buffer 5 is sent from the external device 9 as a character code,
The PU 1 selects print data representing the print bit of the character corresponding to the character code from the ROM 2 and develops it in the print data line buffer 7. In this character development, the high-density detection circuit 6 is operated to set the printing speed of one print line corresponding to high-density printing.

FIG. 5 shows the storage state of character data in the ROM 2. Each character data is the conventional print data A1, A2,
In addition to A3, B1, B2, B3,..., The printing speed corresponding to each printing mode is stored as data for each character. In FIG. 5, the first printing speed corresponding to the printing mode 1 is set for the character "A", the second printing speed corresponding to the printing mode 2 is set, and the third printing speed corresponding to the printing mode 1 is set for the character "B". , A fourth printing speed corresponding to the printing mode 2 is set. In the embodiment, the printing speed according to the printing mode is made different for each character. However, the same data may naturally be used.

FIG. 3 shows a flowchart of a control method of the high-density print detection circuit 6. First, a print mode is selected by a control code (step 31). By this selection, the relative address of the read address of the printing speed data with respect to the start address of each character data storage area stored in the ROM 2 is determined. Next, in step 32, a character code is input. Next, the printing speed corresponding to the character code is input by the relative address data (step 33).
Then, it is determined whether the input printing speed is higher or lower than the previously input printing speed (step 3).
4). If it is smaller, the data is rewritten and stored with the currently input printing speed as the minimum printing speed, and if it is larger or equal, the data is not rewritten (step 35). When one determination is completed, the end of the character data of one print line is determined (step 36). When the data determination of one print line is completed, the minimum print speed data is output to the CPU 1 (step 37). As a result, the CPU 1 outputs the minimum printing speed to the head driving circuit 8 and outputs the corresponding moving speed to the carriage driving circuit 8 to perform printing control.

FIG. 2 shows a detailed circuit diagram of the high-density detection circuit. The print speed corresponding to the character code is latched by the input data latch 11 from the ROM 2 via the data bus 17 at the timing of the control signal S1 output from the control signal circuit 10. This data is referred to as data A. In the minimum printing speed data latch, the printing speed data of the first character of one line printing is latched by the control signal S4 as an initial value for determining the printing speed of one printing line. This minimum printing speed data is referred to as data B. The output permission signal of each latch circuit is given by the control signal S2, and the comparator 13 determines the printing speed. The comparator 13 has A <B, A =
B, and outputs three signals of A> B. The three signals are input through the OR gate 15 as a control signal S3 of the control signal circuit 10 as one comparison end signal. Further, three output signals input to the comparator 13 via the inverter 18 are cleared. If the input data A is smaller than the current minimum printing speed data B, an A <B signal is output. This signal rewrites the minimum print speed data via the OR gate 14 as a latch signal for the minimum print speed data.

When one comparison is completed, the control signal circuit 10
Prompts the CPU 1 via the control signal bus 16 to output the printing speed data of the next character code.
To output the next print speed to the input data latch 11. By repeating the above operation, the CPU 1 determines the printing speed data of the character code of one printing line. When the determination is completed, the CPU 1 reads the data of the minimum printing speed data latch, outputs the minimum printing speed to the head driving circuit 8, sets the moving speed corresponding to the minimum printing speed to the carriage driving circuit, and starts printing of one printing line. . The printer performs the above control for each print line in accordance with a print command from the external device 9 and performs printing.

[0018]

According to the printing control method of the serial printer of the present invention, the setting of the printing speed of one printing line corresponding to the local high density can be made with a simple circuit configuration, and the head driving power supply can be used even in the high density printing. The voltage drop in the circuit is reduced, and in particular, in the case of a head using a wire, driving is performed with an appropriate impact force, and the printing quality is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a circuit configuration according to an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of a high-density print detection circuit according to the present invention.

FIG. 3 is a flowchart of a high-density print detection method according to the present invention.

FIG. 4 is an explanatory diagram of a character code table according to the present invention.

FIG. 5 is an explanatory diagram of a character data storage method according to the present invention.

FIG. 6 is an external view of a serial impact printer according to an embodiment of the present invention.

[Explanation of symbols]

 1 CPU 2 ROM (Read Only Memory) 3 Carriage motor drive circuit 4 Paper feed motor drive circuit 5 Input data buffer 6 High density print detection circuit 7 Print data line buffer 8 Head drive circuit 9 External device 10 Control signal circuit 11 Input data latch 12 Lowest Print speed data latch 13 Comparator 14 OR gate 15 OR gate 16 Control signal bus 17 Data bus 18 Inverter 20 Head 21 Print paper 22 Platen 23 Motor 24 Timing belt 25 Carriage

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-141779 (JP, A) JP-A-57-49575 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 19/18

Claims (1)

(57) [Claims] 1. A character data storage means comprising a plurality of character data, each character data having print speed data corresponding to a plurality of print modes in addition to the print data. And a printing speed judging means for reading out the printing speed data of the character data corresponding to each character from the character data storage means and obtaining the lowest one from the character data storage means. Prior to performing the above, a printing speed is determined by the printing speed determining means, and the printing of the printing line is performed based on the printing speed.