JPH0520249A - Data input switching device - Google Patents

Abstract

(57) [Summary] [Purpose] To save the user the trouble of selecting equipment by himself. [Structure] When a data transmission start signal is received from any of a plurality of data output devices, a busy signal is output to another data output device, and when it is determined that data transmission has ended, the other data output device is output. Stop the busy signal to the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data input switching device connected between a plurality of data output devices and one data processing device.

[0002]

2. Description of the Related Art When a data input switching device connected to the input side of a data processing device has a plurality of interfaces, and data output devices are connected to each of them, for example, some data output devices such as computers. Is connected to each interface on the input side of the printer (data processing device), it is necessary for the printer to specify from which device the transmission data is valid, that is, to select the device that receives the data. is there. Conventionally,
The selection of the data output device is performed by the user switching a switch provided on the printer. When this switch is switched, a busy signal is output to devices other than the selected data output device, and data is not output from those devices.

If a function for selecting a data output device is not provided, an error may occur in which data is mixedly received from some data output devices. For example, in the case of the Centronics specification, even if the data output device has data composed of several bytes, the data transmission is divided into 1-byte units, and when the previous 1-byte data is transmitted, There is a slight time gap between the transmission of 1-byte data, and during this period, a mistake may occur in which data is transmitted from another data output device.

[0004]

However, in the switching method using the above switch, data from devices other than the one selected by the user cannot be accepted, and therefore the switch is switched every time the device to which the data is transmitted is changed. There was a drawback that the switching of No. had to be performed.

An object of the present invention is to provide a data input switching device that can automatically select a device for receiving data and save the user's labor for operation.

[0006]

SUMMARY OF THE INVENTION The present invention is a data input switching device connected between a plurality of data output devices and one data processing device, wherein data from any one of the plurality of data output devices is output. A means for outputting a busy signal to a data output device other than the data output device when the transmission start signal is received, a means for judging reception end of data from the data output device, and a data reception end And a means for stopping the busy signal to the other data output device when the determination is made.

[0007]

According to the present invention, when data transmission is started from any of the plurality of data output devices, a busy signal is output to another data output device, and data is transmitted from the other data output device. Will not be done. Then, when it is determined that the reception of the data from the data output device that is transmitting the data is determined, the busy signal to the other data output devices is stopped, so that the data output devices can also transmit the data. Become.

As means for determining the end of data reception from a data output device that is transmitting data, for example, when a data processing device that processes received data outputs a signal indicating the end of a series of operations, a fixed This is the case, for example, when data has not been transmitted for more than the time. When the data processing device outputs a signal indicating the end of a series of operations, it means, for example, when the printer outputs a signal instructing the discharge of print paper.

[0009]

1 is a block diagram of an input switching device according to an embodiment of the present invention, and FIG. 2 is a diagram showing the timing of control signals of the device. The processing apparatus (for example, printer) of this embodiment is provided with two channels of Centronics parallel interface.

In the figure, a first data output device is connected to a first channel of the interface, and a second data output device is connected to a second channel. The connected data output device is, for example, a microcomputer or the like. The input switching device 1 is a part that selects either the first channel interface or the second channel interface. Here, D _{0 to} D ₇ are signal lines representing data to be transmitted, and bars STROBE ₁ , STROBE ₂ and BUSY ₁ , BUSY ₂ are control lines.

Further, the processing end and reset are control lines sent from the CPU (not shown) for controlling the entire printer to the input switching device 1. The processing end signal is the CPU
Is sent when the acceptance processing of the captured data is completed, and the reset signal is a series of processing based on the received signal, for example, the captured data is printed and the discharge instruction of the printed paper is completed. It will be sent at times.

In the input switching device 1, the flip-flops 2 and 3 receive the signal STROBE to raise the set signal and receive the processing end signal to lower the set signal.
The signal of the flip-flop 2 is input to the OR circuit 5, and the signal of the flip-flop 3 is input to the OR circuit 6. The bar STROBE is also input to the arbitration circuit 4. The arbitration circuit 4 is a circuit that arbitrates between two interface channels. When the arbitration circuit 4 receives the bar STROBE ₁ , it outputs “H” to the OR circuit 6 and outputs the bar STR.
When receiving OBE ₂ , it outputs "H" to the OR circuit 5. Further, by receiving the reset signal, the "H" signal to the OR circuit 6 or 5 is returned to "L". Reference numeral 7 is a circuit for fetching data by a signal from the arbitration circuit 4.

With this configuration, for example, when data is transmitted from the data output device connected to the first channel, the data output device outputs D ₀ to D _0.
7 and STROBE ₁ are transmitted, and "H" is output from the flip-flop 2 to the OR circuit 5 and from the arbitration circuit 4 to the OR circuit 6 in the switching device.

As a result, the OR circuit 5 outputs BUSY ₁ and the OR circuit 6 outputs BUSY ₂ to stop the data transmission from the first channel and the second channel.
At the same time, the arbitration circuit 4 commands the data fetching circuit 7 to fetch the data, and the data fetching circuit 7 fetches the data D _{0 to} D ₇ transmitted from the first channel and sends them to the CPU of the printer. The CPU accepts the fetched data and outputs an end signal to the flip-flop 2 when the processing is completed. As a result, the signal to the OR circuit 5 becomes "L", the OR circuit 5 makes BUSY ₁ fall, and data can be transmitted from the first channel.
On the other hand, on the second channel side, the arbitration circuit 4 to the OR circuit 6
However, BUSY ₂ remains “H” because “H” is output.

The above operation is continued until the printer, which is the processing device, completes a series of operations, for example, until the paper is ejected. When the series of operations is completed, the CPU of the processing device outputs a reset signal to the arbitration circuit 4, which causes the arbitration circuit 4 to drop the signal to the OR circuit 6, so that BUSY ₂ becomes “L” and the second The signal from the channel can be accepted.

[0016]

According to the present invention, when data reception from any one of a plurality of data output devices is started, a busy signal is output to another data output device, and the end of reception is determined. By stopping the busy signal at the time of occurrence, there is no mistake that data is received from another data output device while receiving data from one data output device, and data interference can be prevented. In this way, by automatically outputting a busy signal to other data output devices other than the data output device that is receiving data, it is not necessary to switch using a switch, and operability is improved. No defects will occur.

[Brief description of drawings]

FIG. 1 is a block diagram of an input switching device according to an embodiment of the present invention.

FIG. 2 Time chart of the device

[Explanation of symbols]

 1 Input Switching Device 2,3 Flip-Flop 4 Arbitration Circuit 5,6 OR Circuit 7 Data Acquisition Circuit

Claims (1)

Claim: What is claimed is: 1. A data input switching device connected between a plurality of data output devices and one data processing device, wherein data transmission is started from any one of the plurality of data output devices. When a signal is received, a means for outputting a busy signal to another data output device other than the data output device, a device for determining the end of data reception from the data output device, and a device for determining the end of data reception And a means for stopping a busy signal to the other data output device when the data input switching device is operated.