JPH05165583A - Port switchihg device - Google Patents

Abstract

PURPOSE:To surely perform port switching by preventing a state that data are transferred simultaneously from a host computer from occurring. CONSTITUTION:An on-line state and a ready state are set setting an I/O port 11a as a receivable port, and reception latency time Tr is set on a counter 13 in such state, and preparation for port switching is performed when no data is transferred from the host computer during that time, then, the I/O port 11a is set in a busy state. At that time, transfer monitoring time Tb is set on a counter 14, and the presence/absence of data transfer from the host computer is detected during that time, and data reception processing is performed by returning the I/O port 11a to the ready state when the data is transferred, and also, the next I/O port can be received by setting the I/O port 11a in an off-line state when no data is transferred.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a port switching device applied to a data processing device such as a printing device having a plurality of I / O ports.

[0002]

2. Description of the Related Art Conventionally, in a printing apparatus having a plurality of I / O ports, in a data reception waiting state, first, all ports are set to a ready state, and in this state, print data from the host computer is first read. Starts a series of data processing (print processing) with the received port as an available port, sets the other non-selected ports to the offline state, completes a series of data processing (print processing) for the available ports, and then restarts all ports. Port switching processing such as returning to the original state.

[0003]

However, in the conventional port switching method as described above, data is transferred from the host computer at the same time because all the ports are in the ready state until the usable port is selected. There was something that came. Therefore, a priority control circuit or the like for selecting a specific port is required, which complicates the circuit configuration and causes a problem that the host computer connected to the non-selected port has to retransmit data. It was

The present invention has been made in view of the above points, and can prevent a situation in which data is simultaneously transferred from a host computer and can reliably switch a plurality of I / O ports. The purpose is to provide a device.

[0005]

SUMMARY OF THE INVENTION The present invention provides a plurality of I / Os.
The port switching means for switching the receivable port among the ports is provided, and the presence or absence of data transfer from the host computer is detected at the time of port switching by this port switching means. As a result, if there is no data transfer, the above port The port switching by the switching means is enabled, and when there is data transfer, the port switching by the port switching means is disabled and the original port switching state is restored.

[0006]

According to the above configuration, when data is transferred from the host computer before switching the receivable port, the original port switching state is set. As a result, the data transferred during that time can be received, and as a result, it is possible to prevent the situation in which the data is simultaneously transferred from the host computer.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A port switching device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration.
This device is provided with a plurality of I / O ports 11a, 11b ... And is configured to selectively receive data from a plurality of different host computers. C
The PU 12 controls the entire apparatus, and here executes the port switching processing shown in FIGS. 2 and 3. Under the CPU 12, the counters 13 and 14 respectively count a reception waiting time Tr and a transfer monitoring time Tb necessary for a port switching process described later. The reception buffer 15 stores the data obtained through the I / O ports 11a, 11b, ....

Further, Oa and Ob are online / offline signals, which indicate an online state at the "H" level and an offline state at the "L" level. The online state is a state in which data transfer with the host computer is possible. The offline state means a state in which data transfer with the host computer is impossible (signal disconnection state due to an error or the like). Ba and Bb are busy / ready signals. In this case, the busy state is set at the "H" level,
When it is at "L" level, it indicates a ready state. The busy state is a reception prohibited state. The ready state is a reception permitting state. Here, before describing the operation of the embodiment, the port switching method of the present invention will be described with reference to FIG.

As shown in FIG. 5, for example, two ports A
And B, and each port A, B has a host A,
When B is connected, basically, one of the ports A and B is set in a receivable state (hereinafter, referred to as “blue” state for easy understanding) and the other in a non-receivable state (hereinafter,
In order to make it easier to understand, it is called "red" state) and the receivable ports are sequentially switched. If the data transfer speed of one of the hosts A and B connected to each port A and B is slower than that of the other, the receivable port is switched during data transfer, and data from other hosts is also transferred during that time. May be transferred.

That is, assume that, for example, the port A is in the "blue" state, and the host A that confirms this has transferred the data. Before the data of this host A reaches port A,
When the predetermined switching time has elapsed and the port B is in the "blue" state, the host B that confirms this transfers the data, and as a result, the hosts A and B simultaneously transfer the data. .. In this case, the data of the host A cannot be accepted, and the transfer is re-transferred.

Therefore, in the present invention, when the receivable port is switched, by detecting whether or not there is data transfer from the host computer for a predetermined time (Tb), if there is data transfer, the original port switching state is set. Characterized by returning. That is, in the example of FIG. 5, port A
-B is first set to the "blue"-"red" state and then immediately switched to the "red"-"blue" state. Wait for the data transfer from the host A for the time. If there is data transfer during that time, the port is switched back to the "blue"-"red" state, and if there is no data transfer, it is switched to the "red"-"blue" state. As a result, it is possible to prevent a situation in which data is transferred from the host computer at the same time, and to perform switching efficiently.

Next, the operation of the embodiment will be described with reference to FIGS. 2 and 3 are flowcharts for explaining the port switching processing operation of the embodiment, and FIG. 4 is a timing chart for explaining the port switching processing operation.

The CPU 12 firstly detects the I / O port 11a.
Is designated as a receivable port, the online / offline signal Oa is set to the "H" level, the busy / ready signal Ba is set to the "L" level, and the I / O port 11a is set to the online state and the ready state (steps S1 and S2). .. In this state, the CPU 12 causes the counter 13 to receive the reception waiting time T.
r is set (step S3), and it is checked whether or not data is transferred from the host computer during this Tr (step S4). If there is data transfer, the data is stored in the reception buffer 15. After performing the data reception process (step S5), the processes from step S3 are executed again.

On the other hand, if there is no data transfer even after the reception waiting time Tr has passed (step S6), the CPU 12 enters port switching preparation and sets the busy / ready signal Ba to "H".
After setting the level to make the I / O port 11a busy (step S7), the transfer monitoring time Tb is set in the counter 14 (step S8), and whether data is transferred from the host computer during this time Tb. It is checked whether or not (step S9).

If there is data transfer during the transfer monitoring time Tb, the CPU 12 sets the busy / ready signal Ba to "L" level to return the I / O port 11a to the ready state (step S10), and the data is transferred. Is received (step S11), the processes from step S3 are executed again. If no data is transferred even after the transfer monitoring time Tb has passed (step S12), the online / offline signal Oa is set to the "L" level and the I / O port 11
a is set to the offline state (step S13), and then I /
By designating the O port 11b as a receivable port (step S14), the processing from step S1 is repeated.

As described above, before the receivable port is switched (before the offline state), it is in the busy state,
When data is transferred from the host computer, it returns to the ready state and returns to the original port switching state. As a result, the data transferred during that time can be received, and as a result, it is possible to prevent the situation in which the data is simultaneously transferred from the host computer.

[0018]

As described above, according to the present invention, the presence / absence of data transfer is detected before the receivable port is switched, and the original port switching state is restored if there is data transfer. It is possible to reliably switch a plurality of I / O ports by preventing a situation where data is transferred at the same time. Therefore, in a data processing device such as a printing device having a plurality of I / O ports, data from a plurality of different host computers can be selectively selected without requiring a priority control circuit or the like for selecting a specific port. Can be reliably received and processed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a timing chart for explaining the operation of the embodiment.

FIG. 5 is a diagram for explaining a port switching method according to the present invention.

[Explanation of symbols]

11a and 11b ... I / O ports, 12 ... CPU, 1
3 and 14 ... Counter, 15 ... Receive buffer, Oa and Ob ... Online / offline signal, Ba and Bb
… Biz / ready signal.

Claims (1)

[Claims] 1. A plurality of I / O ports for receiving data transferred from a host computer, a port switching means for switching a receivable port among the respective I / O ports, and a port switching by the port switching means. In this case, a detection means for detecting whether or not there is data transfer from the host computer, and as a result of this detection means, if there is no data transfer, the port switching by the port switching means is enabled,
A port switching device comprising: a control unit that invalidates the port switching by the port switching unit when the data is transferred, and restores the original port switching state.