JPS5952344A - Dot printer controller - Google Patents

Abstract

PURPOSE:To prevent previously the burning of a dot printer due to a program runaway which is caused by a voltage fault, the destruction of a memory, etc., by keeping the dot printer under an ON state. CONSTITUTION:When the dot information is fed to an I/O interface 18 from a CPU10, the interface 18 latches a strobe signal of prescribed timing and at the same time delivers a dot output signal (A) to a driver 20. If a latch output is obtained at a time point t=t0, this output is applied to a time limiting circuit 24 in the form of a dot ON signal for triggering. The circuit 24 applies an output to the driver 20 as a gate signal (B) for a prescribed time T. The driver 20 supplies a dot output signal (A) existing within a dot ON enable time corresponding to the time T to a printer 22 in the form of a dot output (C). If a program runaway occurs due to a voltage fault, the destruction of a memory 14, no latching is carried out to the dot information at that time point by the strobe signal. Therefore, the circuit 24 is not actuated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dot printer control device, and more particularly to a dot printer control device suitable for printing on time cards such as electronic time recorders controlled by a microcomputer or the like.

FIG. 1 shows an outline of a conventional dot printer control device. In the figure, 1o is a central processing unit cPU that monitors the overall system control, 12 is a ROM in which a system program including print information is stored, and 14 is a memory area used for temporary storage of data and a predetermined register. R△~1.16 is lotus, 1'8LtCPLJ10.
Connecting a microcomputer system consisting of ROM 12, RAM 14, etc. to an external dot printer 1
-rur,'.

It is an interface. Predetermined driver i information is input to this T10 interface 18 from the ROM 12 or RAM 14 under the supervision of the CPU 10, and the driver 20 is operated by the output thereof.
The dot printer 22 is driven by the dot output from the dot printer 22, and the dot printer 22 is configured to perform desired printing on a printing medium such as a time card. By the way, the above I10 interface usually includes a latch circuit 18 as shown in FIG.
L is provided, the input dot information is latched or sampled at a predetermined timing, and the driver 20 is driven by the latched or sampled output, thereby stabilizing the printing operation. The one shown in Figure 2 is a D type flip 70
The input terminal 1a is a well-known latch circuit 18L using a knob.
An input D (dot information) is supplied to the input terminal 1b, and a strobe signal T, which is a latch or sample timing signal, is supplied to the input terminal 1b, and Q and Qtf are obtained as outputs. Referring to FIG. 3, for example, assuming that the input is as shown in FIG. 3A and the strobe signal T is as shown in FIG. (for example, from H to L), it occurs in synchronization with that. Note that the falling point of the latch output Q is of type D, so it is the next state change point due to manual effort.

In this way, conventional devices try to stabilize the printing operation by latching the input dot information, but due to voltage fluctuations such as a drop in the power supply voltage, memory corruption, etc., the CPU 10 is unable to perform the printing operation. If a runaway occurs in a program that is specified, the dot information, that is, the input signal in Figures 2 and 3 may remain in the H' or ``L° state, or the waveform may be disturbed and latched by the strobe signal T. If the driver 2 is disabled or the latch is incomplete, the data based on the runaway program
In some cases, a signal is applied via 0 to turn the printer 22 on for a long period of time. As a result, the printer 22 may burn out, which is dangerous, and it is difficult to repair the printer, especially in the case of a small printer used for printing electronic time recorders and integrated with other equipment. there were.

31 The present invention has been made in view of the above points, and aims to prevent the accident in which the dot printer is kept in the ON state due to runaway of the program caused by voltage fluctuation or memory destruction, resulting in burnout. The purpose of the present invention is to provide a dot printer type 1llI device that makes it possible to do this.

In order to achieve this objective, the present invention operates a timer circuit connected between the interface and the dot printer driver when the dot information input from the CPLJ side to the interface can be sampled at a predetermined timing. The present invention is characterized in that the driver supplies dot output from the printer head for a predetermined period of time, and when the driver information cannot be sampled, the dot output is supplied.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 4 is a block diagram showing a schematic configuration of an embodiment of a dot printer control illumination device according to the present invention, and the same reference numerals as in FIG. 1 indicate the same parts and the explanation thereof will be omitted. In the present invention, a time limit circuit 24 having a predetermined time limit, such as a one-john multi of the 1'-Riga type, is provided between the I and 'O interfaces 18 and the 4-driver 20.
The output of this timer circuit 24 is used as a gate signal to determine whether or not to supply the dot information from the 10 interface 18 to the driver 20.

Since it is configured as above, I10 from the CPU side
Assume that the driver I/output signal supplied to the driver 20 has a waveform as shown in FIG. 5A based on the dot information input to the interface 18. At this time, r
,,/o In the interface 18, the latch circuit 181- shown in FIG.
・Latch or 1 non-pull with lobe signal @T. If the latch output rises at time t=tQ, the one-shot multi circuit constituting the timer circuit 24 is triggered using the latch output as the driver hON signal.

As a result, the one-shot multi 24 supplies the output as a gate signal to the driver 20 for a predetermined time period T=t2-tO, as shown in FIG. 5B.

As a result, the driver 20 drives the printer 22 by converting the dot output signal within the ON possible time corresponding to this time limit T into a dot output as shown in FIG. 5C.

The pulse width of the dot output in this case is (tl-to).

In one embodiment of the present invention, the time limit circuit 24 is operated only when the dot information can be latched or 1 non-pulled by the strobe signal T of the latch circuit 18L as described above.
Using the output of this timer circuit 24 as a gate signal, I,'
The printer 22 is driven by using the driver 1 output signal from the O interface 18 as a dot output. Therefore,
Even if the program runs out of control due to bit loss in the memory area of the RAM 14 or when the power supply voltage drops below the specified value, the dot information at that time will not be latched by the strobe signal T, and therefore the time limit circuit 24 will not latch the dot information at that time. is not triggered, and the driver 20 does not supply the dot output signal to the printer 22 as a dot output, so it is possible to prevent the printer 22 from continuing to be in an ON state based on the program and turning into the -C printing 10 beforehand.

In particular, when such a circuit according to the present invention is applied to control a small dot printer built into an electronic time recorder, a single hardware component such as the one-shot multi 24 is added to the conventional circuit configuration. Therefore, there are no space constraints.

In addition, as mentioned above, dot printers like this are integrated into traditional equipment, requiring repairs in the event of burnout, but this is extremely effective as it eliminates such trouble. be.

In the above embodiment, the latch circuit 18L is used as a means for lean-pulling the dot information, and the output thereof is used to operate the timer circuit 24, but other sampling means may also be used, and the timer circuit 2824 may also be of the trigger type. It is also possible to use a timer other than one-shot multi.

As described above, the present invention has an excellent feature of being able to reliably prevent an accident in which a dot printer is kept in an ON state due to a runaway program, resulting in burnout, with an extremely simple circuit configuration. have

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an overview of a conventional dot printer control device, FIG. 2 is a circuit diagram showing a latch circuit provided at the j10 interface in FIG. 1, and FIGS.
Figure C is a timing chart showing an example of the operation of the latch circuit in Figure 2, Figure 4 is a block diagram of an embodiment of the dot printer control device according to the present invention, and Figures 5A to 5 are
This is a timing chart F-1- showing an example of the operation of each part of the device shown in the figure. 10...CPU, 12...ROM, 14...
・RAM, 18...I10 interface, 18
L... Latch circuit, 20... Driver, 22...
...Dot printer, 24...Timed circuit. Patent applicant Amano Co., Ltd. 8- -244- 010

Claims (3)

[Claims] (1) In a dot printer control device that operates a driver via an interface based on predetermined dot information under the supervision of a central processing unit, and drives the printer with dot output from this driver to print desired marks on a printing medium. , when the dot information input to the interface can be sampled at a predetermined timing by a sampling means, a time limit circuit connected between the interface and the driver is operated to allow the dot information to be input from the driver to the printer for a predetermined period of time. A dot printer control device configured to allow dot output to be supplied to a dot printer. (2) The dot printer control Xl device according to claim 1, wherein the sample means is a latch circuit provided in the interface. (3) The dot printer control device according to claim 1 or 2, wherein the timer circuit is one-shot/multiple.