JPH11157173A - Printer control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer control circuit in which noise signal can be prevented through a simple structure. SOLUTION: At such a timing as input of synchronization signals (vertical and horizontal synchronization signals VCYNC, HSYNC) from a printer 3 can be predicted, a switching section 12 is switched to input these synchronization signals VCYNC, HSYNC to a clock generating section 11. At such a timing as input of the synchronization signals VCYNC, HSYNC from the printer 3 can not be predicted, the switching section 12 is switched to interrupt input of these synchronization signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer control circuit for controlling a printer.

[0002]

2. Description of the Related Art A printer control circuit for controlling a printer engine functions as an interface circuit interposed between a host and a printer, and image data to be printed from the host is transferred to the printer via the printer control circuit. Is done.

In this case, the printer control circuit fetches a vertical synchronizing signal and a horizontal synchronizing signal from the printer so as to synchronize with the printing operation in the printer, and synchronizes with the synchronizing signals, that is, these synchronizing signals. And an operation clock for image data transfer is generated by a clock generation unit based on the detection timing. Then, the image data transmitted from the host is transferred to the printer according to the generated operation clock.

[0004]

As described above, the operation of transferring image data to the printer and the operation of printing by the printer are synchronized. However, when the vertical synchronizing signal and / or the horizontal synchronizing signal include a noise signal, transfer of image data to the printer is started at an incorrect timing which is not synchronized with the printing operation of the printer, and accurate printing is performed. There is a problem that processing cannot be performed.

As a countermeasure to solve such a problem, an attempt has been made to prevent a noise signal by providing a Schmitt circuit or a capacitor, but this is not so effective. Also, when a clamp diode is also provided, a remarkable noise prevention effect cannot be obtained.

The present invention has been made in view of such circumstances, and at a timing when it is predicted that a synchronization signal from a printer will not be input, the input of the synchronization signal to the clock generation unit is cut off to achieve a simple operation. It is an object of the present invention to provide a printer control circuit that can prevent a noise signal that is mistaken for a synchronization signal with a configuration.

Another object of the present invention is to provide a printer control circuit which can be used even when a synchronous signal is not output from a printer by inputting a synchronous signal generated by an external device. .

[0008]

According to a first aspect of the present invention, there is provided a printer control circuit for controlling a printer, comprising: means for taking in a synchronization signal from the printer; and generating a clock in accordance with the taken in synchronization signal. Means for connecting the input of the synchronizing signal to the generating means at the timing when the acquisition of the synchronizing signal is predicted, and means for cutting off the input of the synchronizing signal to the generating means at the unexpected timing. I do.

According to a second aspect of the present invention, there is provided a printer control circuit according to the first aspect, further comprising a register connected to the generating means, in which a synchronization signal generated by an external device is written.
When a synchronization signal is not input from the printer, a synchronization signal is input from the register to the generation unit.

According to a third aspect of the present invention, in the printer control circuit according to the first or second aspect, the switching operation of connection / disconnection of the input of the synchronization signal to the generating means is controlled based on a control signal from an external device. It is characterized by having comprised in.

In the printer control circuit according to the present invention, the line to which the synchronization signal from the printer is input is not always kept on, but the input is switched on / off. In other words, at a timing when it can be determined that a synchronization signal is input from the printer, the input of the synchronization signal is turned on, and the clock generation means detects an edge of the synchronization signal from the printer and generates a clock. At a timing when it can be determined that the synchronization signal is not input, the input of the synchronization signal is turned off. As described above, since the input of the synchronization signal is cut off at the timing when the acquisition of the synchronization signal is not expected, there is no possibility that the noise signal is mixed, and the image data is transferred to the printer at an incorrect timing due to the mixing of the noise signal. Can be prevented.

In the printer control circuit according to the present invention, one of the inputs to the clock generating means is connected to a register, and a synchronous signal generated by an external device is written in the register. I have. Therefore, if the printer control circuit inputs the synchronization signal from the register, even when the synchronization signal is not output from the printer,
A clock can be generated by a synchronization signal from this register.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a configuration diagram of a printer device including a printer control circuit of the present invention. In FIG. 1, 1 is a printer control circuit of the present invention, 2 is a host as an external device, and 3 is a printer. The printer control circuit 1 has a bus 10 connected to a system bus 21 from the CPU 20 of the host 2. The bus 10 includes a clock generator 11, a switching controller 13, a first register 14, and a second register 14.
15, an image data processing section 16 and a printer I / F section 17 are connected. The printer control circuit 1 has a switching unit 12 for switching an input to the clock generating unit 11 in addition to the hardware. The switching unit 12 has four input terminals a, b,
c and d and two output terminals A and B.

The clock generator 11 detects edges of the input vertical synchronizing signal VSYNC and the horizontal synchronizing signal HSYNC, respectively, generates a clock EXCLK, and sends the clock EXCLK to two line buffers 31, 31 for storing image data. Output.

The first register 14 is written with the horizontal synchronizing signal HSYNC generated by the host 2, and the second register 15 is written with the vertical synchronizing signal VSYNC generated by the host 2. The output side of the first register 14 is the input terminal d of the switching unit 12.
The output side of the second register 15 is connected to the input terminal c of the switching unit 12. The input terminals a and b of the switching unit 12 are both connected to the printer 3, and a vertical synchronization signal VSYNC from the printer 3 is input to the input terminal a.
The horizontal synchronizing signal HSYNC is input from the printer 3 to the printer.

The switching section 12 connects the input terminal a to the output terminal A, and connects the input terminal b to the output terminal B (first state).
, Input terminal c and output terminal A, input terminal d and output terminal B
Is switched to the state (second state) in which is connected. The switching timing is controlled by a switching control signal from the switching control unit 13. Specifically, the first state is selected at a timing when a synchronization signal is expected to be input from the printer 3, and the second state is selected at a timing when a synchronization signal is expected not to be input from the printer 3.

The image data processing section 16 alternately outputs the image data to be printed transferred from the host 2 line by line to the line buffers 31, 31. Each line buffer 3
Reference numerals 1 and 31 store the input one-line image data,
The stored one-line image data is output to the printer 3. The process of alternately writing image data to the line buffers 31 and the process of alternately reading image data from the line buffers 31 and 31 are synchronized by the clock EXCLK from the clock generator 11, and are switched. 32,33
Is realized by the switching operation.

The printer I / F section 17 exchanges various signals with the printer 3 such as a ready signal and a start signal to be described later.

Next, the operation will be described. FIG. 2 is a timing chart of each signal for explaining the operation of the printer control circuit according to the present invention, and includes a printer power ready signal (a), a printer control circuit power ready signal (b), a printer ready signal (c), and a start signal. A signal (d), a switching control signal (e) from the switching control unit 13, a vertical synchronization signal VSYNC (f) from the printer 3, a horizontal synchronization signal HSYNC (g) from the printer 3, and image data (h) to be printed. , Page end signal (i).

First, a printer power ready signal indicating power on of the printer 3 is input from the printer 3, and a printer control circuit power ready signal indicating power on of the printer control circuit 1 is returned to the printer 3. Then, when a printer ready signal indicating that the preparation for printing is completed is input from the printer 3, the printer control circuit 1 sends a start signal indicating the start of the printing operation to the printer 3.

From the timing when the start signal is sent, it is expected that a synchronization signal will be input from the printer 3. Therefore, the switching control signal from the switching control unit 13 to the switching unit 12 is set to "HIGH". Input terminal a in switching section 12
And the output terminal A, and the input terminal b and the output terminal B are connected (first state).

The vertical synchronizing signal VSYNC from the printer 3 is supplied to the clock generating unit via the input terminal a and the output terminal A of the switching unit 12.
Entered into 11. In the clock generator 11, the vertical synchronization signal VS
When the falling edge of YNC is detected, a clock EXCLK is generated and output to the line buffers 31, 31. The falling edge timing of this vertical synchronization signal VSYNC is 1
It is time to start printing the page.

Next, the horizontal synchronization signal HSYNC
Is input to the clock generation unit 11 via the input terminal b and the output terminal B of the switching unit 12. The clock generator 11 detects the falling edge of the horizontal synchronization signal HSYNC, and outputs the clock EX.
CLK is generated and output to one line buffer 31. The falling edge timing of the horizontal synchronizing signal HSYNC becomes the printing start timing of the first line. The image data of the first row is sent to one of the line buffers 31 and stored in accordance with the horizontal synchronization signal HSYNC. When the next horizontal synchronizing signal HSYNC is input to the clock generator 11, a clock EXCLK is similarly generated and output to the other line buffer 31, and the image data of the second row is sent to the other line buffer 31. Stored. While the image data of the second line is stored in the other line buffer 31, the image data stored in the one line buffer 31 is sent to the printer 3, and the image corresponding to the image data is printed. Is done. Hereinafter, according to the input of each horizontal synchronization signal HSYNC,
A similar process is repeated.

When a page end signal indicating that one page of image data has been completed is input from the host 2 to the printer control circuit 1, the printer 3 thereafter outputs a synchronization signal from the printer 3 until the next start signal. Is expected not to be input, the switching control signal from the switching control unit 13 to the switching unit 12 is set to "LOW" in synchronization with the falling timing of the page end signal, and the input terminal c is connected to the input terminal c in the switching unit 12. The output terminal A, the input terminal d, and the output terminal B are connected (second state).

As described above, during the period in which the synchronization signal is predicted to be input from the printer 3 (between the start signal is issued and the page end signal is input),
The synchronization signal (vertical synchronization signal VSYNC, horizontal synchronization signal HSYNC) from the printer 3 can be input to the clock generation unit 11.
In a period in which a synchronization signal is not expected to be input from the printer 3 (between the start of driving and the start signal is issued or a period in which a page end signal is input and a next start signal is issued), the printer 3 is turned off. The connection of the input / output terminals in the switching unit 12 is switched so that the input of the synchronization signal from the switch 3 is cut off. Therefore, with a simple configuration, it is possible to prevent noise signals from being mixed, and it is possible to perform correct printing processing while completely eliminating the influence of noise signals.

When the printer engine is an LED printer, a thermal printer, or the like, some printers do not output a synchronization signal. Such a printer cannot be handled by a conventional printer control circuit. However, the printer control circuit of the present invention has a configuration in which the outputs of the first register 14 and the second register 15 to which the horizontal synchronizing signal HSYNC and the vertical synchronizing signal VSYNC generated by the host 2 are written can be taken into the clock generator 11. Even for a printer that does not output a synchronization signal, a clock can be generated using these synchronization signals generated by the host 2, and the printer control circuit of the present invention can be used.

[0027]

As described above, in the printer control circuit of the present invention, the input of the synchronization signal is cut off at the timing when it is predicted that the synchronization signal is not input from the printer. It is possible to prevent the image data from being transferred to the printer at the wrong timing due to the mixing of the noise signal without being mixed, and to perform the correct printing process.

Further, the printer control circuit of the present invention has a configuration in which a register in which a clock generated by an external device is written is connected to one of the inputs to the clock generating means, so that even when a synchronous signal is not output from the printer. , A clock can be generated by the synchronization signal from this register,
It is possible to cope with a printer that does not output a synchronization signal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a printer including a printer control circuit of the present invention.

FIG. 2 is a timing chart for explaining the operation of the printer control circuit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer control circuit 2 Host 3 Printer 11 Clock generation part 12 Switching part 13 Switching control part 14 1st register 15 2nd register

Claims (3)

[Claims] 1. A printer control circuit for controlling a printer, means for taking in a synchronization signal from the printer,
Generating means for generating a clock in accordance with the received synchronization signal, and connecting the input of the synchronization signal to the generation means at a timing at which the capture of the synchronization signal is predicted; Means for cutting off the input. 2. A register connected to the generating means, to which a synchronization signal generated by an external device is written.
2. The printer control circuit according to claim 1, wherein a synchronizing signal is input from said register to said generating means when no synchronizing signal is input from said printer. 3. The printer control circuit according to claim 1, wherein the switching operation of connection / disconnection of the input of the synchronization signal to said generating means is controlled based on a control signal from an external device.