JPH0412073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a literary and graphic information system (view data, This invention relates to a starting circuit for a printer used to make hard copies of still images (teletext, etc.), and is designed to prevent malfunctions, particularly when the terminal is powered on.

In general, text and graphic information systems (teletext, view data, capten, etc.) have been proposed that provide a variety of information in text and graphics using a home television receiver as a terminal and using television broadcast waves or a subscriber telephone line as a transmission line. ing. In such a character/graphic information system, as shown in FIG. 1, a television receiver 1 serving as a terminal receives the character/graphic signal to obtain a still image, and the character/graphic signal is transmitted to the television receiver 1. The character/graphic signals are supplied from the printer 2 to the printer 2, where the character/graphic signals are hard-copied. In this hard copy, the same still image that is displayed on a television screen is printed and displayed as a large number of dots on thermal recording paper using, for example, a thermal head.

By the way, generally when you get this hard copy 1
Character and graphic signals for two still images are sampled and converted into digital data, which is temporarily recorded in a memory, and the read data is used to print one image. In this case, in the printer 2, for example, when printing by moving thermal recording paper, the thermal recording paper is continuously fed by a DC motor, and the vertical scanning direction of the television image is set in the main scanning direction of the thermal head. and
Sampling is performed in a horizontal period, and the sampling phase is shifted by the sampling pitch in the horizontal direction of the television screen every frame.

Recently, in order to control the above-mentioned printer, a central processing unit (hereinafter referred to as
A printer has been proposed in which a printer is equipped with a CPU (called a CPU) and the operation of the printer is controlled by control signals from the CPU. Conventionally, a starting circuit for a printer has a configuration as shown in FIG. That is, in FIG. 2, 3 indicates a CPU that sends a control signal to a printer 2 provided in the television receiver 1, and the control signal from this CPU 3 is sent to the printer 2 via an output port 4. Do as you please. This CPU3
The other control signal is a print command signal that controls the paper feed DC motor of the printer 2, for example.
This is a 6MHz dot clock signal, etc. Matako
In order to prevent malfunction, the CPU 3 is generally configured not to output an output signal until it is initialized (initial value setting). That is, 5 indicates a power supply terminal to which, for example, positive DC voltage is supplied, and this power supply terminal 5 is connected to the power input terminals of the CPU 3, output board 4, etc. via a power switch 6, and this power supply switch 6 is used for voltage division. The resistors 7a and 7b are grounded through a series circuit of resistors 7a and 7b.
is connected to one input terminal of the comparison circuit 8, and the power switch 6 is connected to the other input terminal of the comparison circuit 8 via a time constant circuit 9 consisting of a resistor 9a and a capacitor 9b. In this case, the time constant of the time constant circuit 9 is set to the time for initializing the CPU 3, for example, 0.5 seconds, and when the voltage at the other input terminal of the comparator circuit 8 becomes higher than the voltage at one input terminal, that is, the power switch 6 is turned on. After that, for example, 0.5 seconds later, a reset signal is supplied to the CPU 3 to cancel the inhibition of output from the CPU 3. Reference numeral 10 denotes a video signal input terminal to which a video signal to be hard-copied is supplied. is connected to a power supply terminal +B to which a positive DC voltage is supplied, the emitter of this transistor 11 is grounded via a resistor 11a, and the emitter of this transistor 11 is connected to a copy signal input terminal of the printer 2. Reference numeral 12 denotes a synchronization signal input terminal to which horizontal and vertical synchronization signals of the video signal to be hard-copied are supplied, and the synchronization signal supplied to the synchronization signal input terminal 12 is passed through an amplification circuit 13 to an npn transistor 14. The collector of this transistor 14 is connected to the power supply terminal +B, and the emitter of this transistor 14 is grounded through a series circuit of resistors 14a and 14b.
The synchronization signal obtained at the connection point b is supplied to the synchronization signal input terminal of the printer 2.

In such a printer 2, if the print command signal, that is, the output signal of the output port 4 is a low level signal for 100 msec or more, and a synchronization signal is supplied to the synchronization signal input terminal at this time, the printer 2
At this time, the DC motor for paper feeding rotates and begins feeding the paper and at the same time starts printing. In this case, once paper feeding is started, the printing operation continues for one screen. The television receiver 1 and printer 2 shown in FIG. 1 are otherwise constructed in a well-known manner.

Therefore, when you want to make a hard copy of a still image in such a character and graphic information system, you operate the print button provided on the television receiver 1, and as a result, a print command signal etc. are supplied from the CPU 3 to the printer 2, and this Since the synchronization signal is supplied to the printer 2 through the synchronization signal input terminal 12, the printer 2 starts the paper feeding operation and starts printing, so that a predetermined hard copy can be obtained.

However, in such a character and graphic information system, after turning on the power switch 6 of the television receiver 1, the output port 4 operates on its own, for example, for 0.5 seconds until the CPU 3 initializes, rather than under the command of the CPU 3. Therefore, when the power to the printer 2 is turned on first, and then the power switch 6 of the television receiver 1 is turned on, the output side of the output port 4 receives a low level signal regardless of the command from the CPU 3. In this case, since the synchronization signal is supplied to the synchronization signal input terminal 12, there is a risk that the printer 2 may start printing without permission when the power switch 6 is turned on. There was a problem in that once printing started due to this malfunction, printing continued for one screen.

In view of this point, the present invention is intended to improve the above-mentioned disadvantages.

Hereinafter, one embodiment of the starting circuit for the printer of the present invention will be described with reference to FIG. This third
In the figure, parts corresponding to those in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

In the example shown in FIG. 3, the base of the transistor 14 to which the synchronizing signal is supplied is connected via a diode 15 constituting a switch circuit to the output side of the comparator circuit 8 from which the reset signal is obtained. In this case, the output side of the comparator circuit 8 is configured to be grounded when no reset signal is obtained. In this example, the other configuration is the same as the conventional one.

Since this example is configured as described above, the amplifier circuit 13 is operated for a period of 0.5 seconds, for example, from when the power switch 6 is turned on until the reset signal is obtained at the output side of the comparison circuit 8, that is, from when the power switch 6 is turned on until the CPU 3 is initialized. The synchronizing signal obtained on the output side flows through the diode 15 to the output side of the comparator circuit 8 and is not supplied to the printer 2. Therefore, until the CPU 3 is initialized when the power switch 6 is turned on, the printer 2 will not start paper feeding, printing, etc., regardless of the state of the output side of the output port 4. After the reset signal is obtained on the output side of the comparator circuit 8, that is, after the CPU 3 is initialized, the cathode side of the diode 15 becomes a high level signal, and this diode 15 is turned off, so that the output side of the amplifier circuit 13 The synchronizing signal obtained is supplied to the printer 2 through the transistor 14. Therefore, at this time, when the print button of the television receiver 1 is operated, the printer 2 starts feeding paper, printing, etc. as well as in the conventional case.

As described above, according to the present invention, it is possible to obtain a printer that can produce good hard copies without malfunctioning when the power switch 6 of a powder machine, for example, a home television receiver is turned on.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations may be adopted without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, FIG. 2 is a block diagram showing the main parts of an example of a starting circuit for a conventional printer, and FIG. 3 is a main part of an embodiment of a starting circuit for a printer of the present invention. FIG. 1 is a television receiver, 2 is a printer, 3 is a
CPU, 4 is output port, 6 is power switch, 8
9 is a comparison circuit, 9 is a time constant circuit, 12 is a synchronizing signal input terminal, and 15 is a diode for a switch.

Claims (1)

[Claims] 1. A starting circuit for a printer that starts operation upon receiving a synchronization signal supplied with a video signal and a control signal supplied from a central processing unit, and prints a still image corresponding to the video signal, and is set to a constant state after power is turned on. initializing means for initializing the central processing unit when a time has elapsed; and blocking means for blocking the supply of the synchronization signal to the printer for a period until the central processing unit is initialized by the initializing means. A starting circuit for a printer, characterized in that: