JPH01293460A - Interface switching device - Google Patents

Abstract

PURPOSE:To switch interfaces without applying an unnecessary interruption to a system by switching the interfaces after the confirmation of the unused condition of the both interfaces. CONSTITUTION:Since inputted interfaces 101 are switched by selecting a condition in which they are not under mutual communication by means of a main control part 103 in a printing device 200, they can be switched in the ON- condition of a power source without generating an error condition. Thus, a parameter setting action immediately after turning on the power source is made unnecessary, and since the contents of the memory not to be erased can be held, operability is further enhanced. Consequently, even in the case of the incessant monitor communication of the printer condition such as a printer interface, since the inputted interfaces can be switched while the power source is being the ON-condition, an action such as the resetting of the parameter or the re-execution of a broken-down load to a memory immediately after the ON-condition of the power source is made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an interface switching device for an input/output device having two or more interfaces, such as a Centronics interface and a so-called video interface.

[Prior Art] FIG. 5 shows an example of a conventional interface control device in which an input interface and a direct interface are connected to a normal printing device. An input interface means a connection that converts a code into a font within this control device, and a direct interface means a connection that directly sends dot data to a printing unit.

A host computer 150 is connected to the left side of this interface control device, and a printing device 200 is connected to the right side. First, the input interface section l○1 will be explained.

Text information 121 from an external host computer is loaded into page memory 102 through input interface section 101. The main control unit 103 converts this loaded character code information into dot pattern information by referring to the font memory 104, and converts the loaded character code information to the scan buffer 104.
Stored in 05. The pattern information developed in this buffer 105 is converted into a serial signal by a parallel to serial converter 106,
Image information is sent in a dot pattern to a printing section (not shown) through a multiplexer 107. Other print start commands and the like in the input interface are sent to the printing unit 200 through the multiplexer 108 using the information bus 125.

On the other hand, information from the direct interface 110 passes directly through multiplexers 107 and 108 to the printing section 2.
Sent to 00.

The reason why dot pattern information is sent directly from the direct interface section 110 to the printing section is for applications in which the host computer wants to create and send more complex image data.

Switching between the input interface section 101 and the direct interface section 110 is performed by the switch 301 or immediately after a switching command from the host computer 150.

[Problem to be Solved by the Invention] However, when switching between the above two interfaces, the switching is performed without checking whether or not the interface on the side to be disabled is currently communicating. There is a high possibility that the printing device side or the host computer side will display an error at the moment of switching. If an error occurs, both must be reset.

Of course, the currently commonly used method is to switch both interfaces with the power turned off, but if you turn off the transformer power, you will need to perform operations such as initialization again. etc., which had the disadvantage of being cumbersome to operate.

Conventionally, switching between, for example, the R3-232C interface and the input interface was possible even if the switch was made while the power was on, because communication would be interrupted if the printer was placed offline, for example. However, in the case of a direct interface, the printer's printing unit status (paper presence/absence, ready status)
Since the interface is constantly monitored and communicated, it is very difficult to switch interfaces, and it is very difficult to switch without error while the power is turned on.

Therefore, the present invention is an interface switching device used in a system in which the same input/output device is provided with two or more interfaces, which is capable of switching the interfaces without adding unnecessary interference to the system. This is what we propose.

[Means for Achieving the Object] According to the present invention, at least two or more first
and a second interface, an interface switching device for switching these two or more interfaces to establish one interface between the processing system and an input device or an output device, the interface switching device In switching between the first and second interfaces, the present invention is characterized by comprising a checking means for checking the usage status of both interfaces, and a switching means for switching the interface after confirming the non-use status of both interfaces.

The input interface is switched by selecting a state in which the main control unit in the printing device is not communicating with each other.
Switching can be done without causing a failure state while the power is on.

Therefore, there is no need to set parameters immediately after the power is turned on, and the contents of memory that you do not want to erase are retained.
Operability has been further improved.

[Examples] Examples according to the present invention will be described in detail below with reference to the accompanying drawings.

<Connection> FIG. 2 shows the interface control unit 100 according to the embodiment.
and a host computer 150. 3 is a diagram showing a connection with a printing section 200. FIG. The interface control unit lOO is
By switching between the input interface and the direct interface, one of the interfaces is established between the host computer 150 and the printing unit 200.

<Overall Configuration of Embodiment> FIG. 1 is a block diagram showing details of the interface control unit 100 according to the embodiment shown in FIG. A circuit for inputting text information, converting it into dot pattern information, and sending it to the printing unit 200 is shown.

In FIG. 1, 101 is an input interface section;
02 is a page memory, 103 is a main control unit that controls the entire interface control unit 100, 104 is a font memory, 105 is a scan buffer, 106 is a parallel-to-serial converter, 1o7°1O8 is a multiplexer, 109 is an AND gate, 110 is a direct interface unit.

The direct interface unit 110 converts the character code into predetermined dot pattern information corresponding to the code in the host computer 150, and directly outputs the information to the printing unit 2.
00, and is used for sending dot pattern information directly to the printing unit 200 without using an interface circuit inside the blink.

Next, the case where an input interface is used and the case where a direct interface is used will be explained with reference to the flowchart shown in FIG. Switching between selecting the input interface section 101 and the direct interface section 110 is performed by a command sent from the host computer 150 via the human interface section 101. The control flowchart in FIG. 3 shows a program executed by the main control section 103.

<Selection of input interface> First, text information consisting of character codes etc. is sent from the host computer 150 to the main interface control unit 10.
A case will be described in which the dot pattern is converted into a dot pattern within 0 and printed by the printing unit 200.

Before transferring print data, host computer 1
50 sends an interface selection command to the control unit 100. If this command is to select the input interface section 101, step 82φ in step S4, step S6=>step S8
Proceed to.

Here, the main control section 103 connects an information bus 122 from the direct interface section 110 to the printing section 200, and conversely from the printing section 200 to the direct interface 110.
and the information buses 123 to see if these buses are in use. The information bus 122 includes, for example,
It includes a print command line, a print request line, a paper feed information request line, etc. to the printing unit 200, and it is checked that all of these lines are not in operation. The information bus 123 also includes a ready status signal output from the printing unit 200, horizontal and vertical synchronization signals (HSYNC, VSYNC), and
check that this status bus is not in operation.

The case where the information bus 122 is inactive and the status bus of the print section is not in operation means that the host computer 1
50 indicates that it is not communicating with the printing unit 200. Therefore,
In step S12, the main control unit 103 sets the signal 5ELECT on the signal line 124 to LOW level. In this way, AND gate 109 is closed, thereby sending information to host computer 150 that the direct interface is not ready. Further, in step S14, a response (ACK) indicating that the input interface has been selected is returned. On the other hand, when the select signal 124 is at the LOW level, the multiplexers 107 and 108 select the input on the A side in FIG. 1, that is, the data from the main control section 103.

Incidentally, in step S8, if the input interface 101 is negative, in step S16, a negative response (N
AK) is returned.

The details of the print data transfer performed in step S22 will be described below. An input interface ready signal is sent from the main control unit 103 to the host computer 150 via the signal line 125. For this reason, the host computer 150 sends text information 121 consisting of character codes and the like to the input interface section 101. Text information 121 is then stored in page memory 102. The main control unit 103 sequentially reads character codes from the page memory 102, refers to the font memory 104, converts them into dot memory, and sends them to the scan buffer 105. The scan buffer 105 constitutes a so-called double buffer (105a, 105b), and while one side is writing a dot pattern by the main control unit 103,
The other one is read out, passed through the parallel-to-serial converter 106, passed through the multiplexer 107, and is sent to the printing section 200.

When the dot pattern for the first scan is loaded into the scan buffer 105, the main control unit 103 connects the information bus 1.
A print command is sent to the printing unit 200 through 25. Horizontal and vertical synchronization signals are sent from the printing section 200 via the information bus 123, and the main control section 103 sends a dot pattern to the printing section 200 in synchronization with the synchronization signals.

<Direct Interface Selection> Next, the case of printing on the printing unit 200 via the direct interface 110 will be described. When a command to select the direct interface section 110 is received from the host computer 150, in step S1o, the main control section 103 confirms that the printing section 200 is not performing a printing operation in the same manner as in step S8. , in step S18, the signal 5ELECT is switched to HIGH. This opens the gate 109, so that the information bus 123 from the printing unit 200 is connected to the direct interface unit 110.
is sent as is.

Also, the signal 5ELECT on the same signal line 124 causes multiplexers 107 and 108 to select the information bus 122 and image signal 127 from the direct interface. Further, in step S20, an affirmative response is sent indicating that the bus selection has been completed. Since the printing operation is left to the host computer 150, the explanation will be omitted here.

<Return> The operation of returning the printing initiative to the input interface section 101 is as described above, but before that, the post computer 15 is transferred via the input interface section 101.
It is assumed that a switching command from 0 to the input interface unit side comes.

<Other Embodiments> FIG. 4 shows another embodiment of the present invention, in which the input interface section 101 and the direct interface section 110 are connected even when a switch input command is issued from the operation panel 201.
This makes it possible to switch between

In this case, for example, the signal 202 from the operation panel 201
When is "1", it is set that the input interface is selected, and when it is "O", it is set that the direct interface is selected. If this is done, the control shown from step 86 onward in FIG. 3 can be used almost as is. The operation panel includes an indicator (not shown) that indicates which interface is currently selected. If an operation is performed to change from the currently selected interface to the other interface, step S14. If an ACK response is received in step S20, the display of the interface selected by the operator lights up, but if a NAK response is received in step S16, the display on the display is not reversed.

<Effects of the Embodiment> In the embodiment described above, the input interface is switched by selecting a state in which the main control unit 500 in the printing device is not communicating with each other, so an error state occurs even if the power is left on. You can switch without any problem.

Therefore, there is no need for a parameter setting operation immediately after the power is turned on, and the contents of the memory that do not want to be erased are retained, resulting in a further improvement in operability. In other words, even for interfaces such as printer interfaces that constantly monitor and communicate the status of the printer, it is now possible to switch input interfaces while the power is on, making it easier to reset parameters immediately after turning on the power. There is no need for operations such as downloading or re-downloading to memory.

<Other Modifications> In the embodiments described above, an output device as a printer was used as an example, but other output devices or input devices may be used. Furthermore, various interfaces are possible without departing from the spirit of the present invention.

[Effects of the Invention] According to the present invention described above, switching of input interfaces is performed after confirming that the interface is not in use.
This eliminates unnecessary interactions such as the occurrence of error conditions and resetting after power-on.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention; FIG. 2 is a system connection diagram of the embodiment in FIG. 1; FIG. 3 is a flowchart showing part of a control program according to the embodiment; The figure is a block diagram showing another embodiment of the present invention, and FIG. 5 is a block diagram showing a conventional example. In the figure, 100...interface control unit, 101...input interface unit, 103...main control unit, 107
．． 108... Multiplexer, 109... AND gate, 110... Direct interface, 12
1... Document information, 122, 123, 125... Information bus, 124... Signal line of signal 5ELECT, 150
. . . host computer, 200 . . . printing unit, 2°l . . . operation panel, 202, 203 . Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) In a system in which an external data processing system and an input device or an output device are connected by at least two or more first and second interfaces, by switching these two or more interfaces,
an interface switching device for establishing two interfaces between the processing system and an input device or an output device, comprising: checking means for checking the usage status of both interfaces when switching between the first and second interfaces; An interface switching device comprising: switching means for switching the interface after confirming that the interface is not in use.