JPS63293628A - Printer switching device - Google Patents

Abstract

PURPOSE:To improve the operability and the handling performance of a printer switching device by performing the communication among a printer, a printer switching device and a controller by means of an unused signal line of a printer. CONSTITUTION:A controller 1 for print requiring body of a word processor, etc., and another controller 2 are connected to a printer 4 via a printer switching device 3. This switching device 3 consists of a receiver circuit 5, a driver circuit 6, a selector circuit 7, an inverter 8, and an AND gate circuit 9. Both controllers 1 and 2 are connected to the printer 4 against a single printing request received from said controllers 1 and 2. While the controller 1 or 2 is selected based on a prescribed deciding reference and connected to the printer 4 against >=2 printing requests received from the controllers 1 and 2. Then an unused signal line is applied for execution of communication among the printer 4, the device 3 and both controllers 1 and 2. Thus the switch control can be automatized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printer switching device, and particularly to a printer switching device when a single printing device is shared by a plurality of printing requesters.

[Conventional technology]

Conventionally, printer switching devices used when a single printing device is shared by multiple printing requesters have either been simple devices with a mechanical or electrical switch that can be switched manually, or advanced devices. A print server using a local area network or the like is known as a print server.

Literature related to this type of device includes, for example, Nikkei Electronics (July 6, 1981 issue), pp. 101-13.
On page 5, ``Local networks are actively being commercialized ahead of the approaching period of widespread use.''

[Problem that the invention seeks to solve]

However, the above-mentioned manual switching method has problems such as forgetting to switch, erroneous operation during printing, restrictions on placement such as placing them close to the operator, and structural difficulty in switching between multiple units. When a network or the like is used, the entire system becomes extremely expensive, making it unsuitable for small-scale systems. As mentioned above, the conventional technology does not take into consideration the performance-to-price ratio for mid-range and high-end machines that have a system that includes a print request unit, printer switch, and printing device, resulting in problems in terms of operability and price. was there.

An object of the present invention is to provide a printer switching device that is small-scale but suitable for intermediate and high-end machines.

[Means for solving problems]

The problem described above is that in a printer switching device that follows a plurality of print requester control devices and selects and connects one of the control devices to a subsequent printing device, when a print request from one of the control devices is a determining means that adopts the print request and determines which one to select among the print requests from two or more of the control devices, and connecting the control device to the printing device based on the determination of the determination means. The problem is solved by a printer switching device that communicates with the printing device using an unused signal line among the signal lines provided in the printing device.

[Effect]

A printer switching device is provided following the plurality of print requesting body control devices, and a printing device is connected to the printer switching device, so that in response to a print request from one of the control devices, the control device is switched to the printing device. When there is a print request from two or more of the control devices, one of the control devices is connected to the printing device based on predetermined criteria. Communication is performed using unused signal lines provided in the printing device.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a block diagram of this embodiment.

1 is a control device for a print requesting body such as a word processor, 2 is a control device for another word processor, etc., 3 is a printer switch according to the present invention, 4 is a printing device (printer), and 5 is a receiver circuit shown collectively. For example, a Schmitt gate circuit of a logic circuit, 6 is a driver circuit written collectively, for example an open collector type buffer gate circuit of a logic circuit, 7 is a selector circuit, for example a data selector circuit of a logic circuit, 8 is an inverter, 9 is an AND gate circuit. Printer signal INI from control device 1
is connected to the input A of the selector 7 via the receiver 5, and the printer signal IN2 from the control device 2 is connected to the input of the selector 7 via the receiver 5'. The selector 7 outputs input A to output Y when the signal at input S is low level (0 level of the logic circuit), and outputs input B to output Y when the signal is high level (level of the logic circuit). Printer switching request signal (hereinafter referred to as request signal) REQI from the control device 1
is applied to the input S of the selector 7 via the inverter 8 to switch the selector 7, and at the same time passes through the inverter 8' to the control device 2 as a printer switching device busy signal (hereinafter referred to as "busy signal") BUSY2. Similarly, the printer switching request signal REQ2 from the control device 2 becomes the busy signal BUSYI to the control device 1 via the AND gate 9. In this embodiment, the control device 1 has priority, but the priority has no meaning and is for the purpose of simplifying the circuit configuration.

Control device i! The output signals (printer signals) INI and IN2 from 1 and 2 are the input signal INO of the printing device 4, and the input signal (printer signal 0UTI) to the control devices 1 and 2.
, 0UT2 is the output signal from the printing device 4 ○UTO is
The pin numbers and signal specifications of the interface connectors are also the same. request signals REQI, REQ2 and busy signal BUSYI.

BUSY2 is assigned an unused pin number as an interface of the printing device 4.

The control device 1 is configured as described above, and the printer switching flowchart is shown in FIG.
B) 51, the print request (FB5
3), control bag @1 checks whether the busy signal BUSYI is active (FB54). BUSY
If I is inactive, the printer switch 3 is unused and the request signal REQI is made active (FB55).
. After the circuit operation time has elapsed (FB56), confirm that BUSYI is inactive (FB57). This is to avoid collisions when accesses from the control device 2 occur simultaneously.

If BUSYI is active, REQI is set (FB58) to return to the initial state, and the control device 1 displays a message to the operator and enters an input waiting state (FB52). If BUSYI is inactive on FB57,
Since the printer switch 3 becomes usable, print data is sent to the INI line, and printing is executed by the printing device 4 (FB59).

When printing is completed (FB60), request signal REQI
Please reset FB61) to return to the initial state and end.

The above description has been made regarding the control device 1, but the same applies to the control device 2. Furthermore, it goes without saying that the same flow can be applied even when there are a large number of control devices.

According to this embodiment, there are only two printer switching control signals, which makes the configuration extremely simple, and can be handled by adding and changing a small portion of the printer interface of the control device, resulting in an inexpensive configuration. Furthermore, since there is no memory circuit within the printer switch, there is no possibility of malfunction when the power is turned on or due to external noise.

By the way, the interface of a printing device (printer) generally uses signal specifications based on the interface signal commonly called the Centronics interface proposed by Centronics Corporation of the United States, and uses a 36-core connector and cable. . These 3
All six signal lines are never used, and usually at least two to three are unused. The present invention has focused on this point, and is configured to automatically switch printers by sending a signal for controlling switching of the printer switching device from the control device to the printer switching device using an unused line. . As a result, there is no need to make any modifications to the printing device, so the conventional printing device can be used as is. In addition, switching control uses a use request signal (REQ signal) and an in-use signal (
Because of the simple control using the BUSY signal, the printer switch can be configured with only logic circuits.

FIG. 3 shows another embodiment. In this embodiment, the line from the changeover switch 11 for manual changeover provided in the printer changeover device 3 itself and the changeover control signal REQ from the control devices 1 and 2 are shown.
, BUSY line can be used as a printer switch for conventional systems by switching between manual and automatic modes.6 According to this embodiment, the service is compatible with both automatic and manual systems. Improves sex.

According to the two embodiments described above, it is possible to automate the switching control of the printer switching device without changing the interface of the printing device, and the operability and ease of handling are greatly improved. Since the interface of the printing device has not been changed, the conventional printing device can be used as is, making it highly versatile.

Switching control is simple control at the logic circuit level, which simplifies the configuration of the control device, and when a printer switch is not used, the control device and printing device can be directly connected and used as before, making it easier to use conventional systems. can be used as is.

〔Effect of the invention〕

A printer switching device is provided between the plurality of print requesting body control devices and the printing device, and when print requests from two or more of the control devices are received, any one of the control devices is selected as the printing device based on a predetermined criterion. However, communication between the printing device, printer switcher, and control device is performed using unused signal lines on the printing device, so there is no need to change the interface of the printing device (you can use the conventional printing device as is). This has the effect of automating printer switching control and providing excellent operability and handling.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
The flowchart in FIG. 3 is a block diagram of another embodiment.

Claims (1)

[Scope of Claims] 1. In a printer switching device that follows a plurality of print requestor control devices and selects and connects one of the control devices to a subsequent printing device, printing from one of the control devices a determining means that adopts the print request in response to the request and determines which one to select among the print requests from two or more of the control devices; 1. A printer switching device comprising a switching device connected to a printer, and communicating with the printing device using an unused signal line among signal lines provided in the printing device. 2. The printer switching device according to claim 1(1), wherein the determining means and the switching means consist only of logic circuits. 3. The printer switching device according to claim 1 or 2, wherein the determining means and switching means include manual determining means and switching means and switch between manual and automatic.