JPS62117440A - Communication controlling system - Google Patents

Abstract

PURPOSE:To quickly discriminate the receiving state of a communication partner and determine the propriety of communication, by adapting a constitution which checks the state of the communication partner after dividing the state into two stages. CONSTITUTION:The 1st transmission means M1 which sends a transmission starting signal before data signals, 1st detecting means M2 which discriminates whether or not a reception ready signal is obtained from a communication partner within the 1st waiting time after the transmission starting signal is sent, 2nd transmission means M3 which sends a prescribed message signal when the reception ready signal is not obtained, and 2nd detecting means M4 which discriminates whether or not a response signal is obtained to the message signal within the 2nd waiting time after sending the message signal, are provided. Therefore, data transfer is stopped when no response signal is obtained from the communication partner and data transfer is started when a response signal is obtained from the communication partner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication control system, and particularly relates to an improvement in handshake at the start of data communication.

[Conventional technology]

In conventionally known data communication devices, signals are exchanged between the communication devices according to a predetermined protocol.

Generally, as a handshake at the start of data communication, the transmitting side sends a data communication start signal (ENQ signal) to the receiving side, the receiving side receives this signal, and when the data reception is completed, a so-called ACK signal is sent to the transmitting side. is being sent back to. After confirming this ACK signal on the sending side,
Data transmission begins. After that, a predetermined amount of data (
For example, when data for 80 characters is transmitted, the above-mentioned /% endshake is executed again, and the predetermined amount of data is further transmitted.

[Problem that the invention seeks to solve]

However, in recent years, terminal devices that can be used for multiple purposes have appeared, and some of them do not have the function of sending back an ACK signal in response to the above-mentioned data communication start signal (ENQ signal).

When performing data communication with such terminal equipment, for example, when communicating between a main computer and a certain terminal, when an ACK signal is not sent back in response to sending a communication start signal (ENQ signal), In some cases, a predetermined portion of data (for example, 80 bytes) is forcibly sent after a certain waiting time (for example, 5 seconds) has elapsed. In this case, the communication start signal (EN
Q signal) and waiting for a certain period of time.

Other systems are configured to immediately transfer data and use TTP without performing the handshake described in 1-1 (XON on the terminal side,
Depending on the power-on state of the terminal and the connection state of the transmission cable, this may result in unnecessary data transfer.

In this way, data communication with a device that does not have a handshake function for starting communication requires extra time and effort, and the transmission efficiency is extremely reduced. .

Therefore, an object of the present invention is to provide a communication control method that allows efficient data communication to be performed even with various terminal devices.

[Means for solving problems]

In the communication control system according to the present invention, if the reception ready signal cannot be received from the communication partner within the first waiting time after sending the transmission start signal sent before the data signal, a predetermined message signal is sent. and starts transmitting the data signal when a response signal to the message signal is received within the second waiting time.

〔Example〕

Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a block diagram showing an embodiment of a communication device to which the present invention is applied. This embodiment includes a first transmitting means M1 that transmits a transmission start signal prior to a data signal, and a communication phase f within a first waiting time after transmitting the transmission start signal.
a first detecting means M2 for determining whether or not a receiving ready signal has been obtained from the receiver; a second transmitting means M3 for transmitting a predetermined message signal when the receiving ready signal is not obtained; a second detection means M4 for determining whether or not a response signal to the message signal is received within a second waiting time after sending the signal, and when no response signal is obtained from the communication partner; Data transfer is stopped, and when the response signal is obtained from the communication partner, data transfer is started.

Note that when receiving a reception preparation completion signal from the communication partner within the first standby time, data transfer is immediately started.

FIG. 2 is a schematic configuration diagram showing an embodiment of a communication system to which the present invention is applied. In this embodiment, the host computer HC and the terminal devices TA, TB,
It is connected to TC. Regarding the communication transfer rate, the host computer HC and each terminal device TA, TB
, TO.

FIG. 3 is a block diagram showing the configuration of FIG. 2 in more detail. As is clear from the figure, the data transfer procedure is controlled via the serial interface S. Also, transfer data is transferred from memory to I10 under the control of the CPU.
Serial interface S via the control circuit
Sent to I. However, the transfer from the memory to the serial interface 91 is performed after the handshake described below is completed.

FIG. 4 is a flowchart showing the operating procedure of this embodiment, that is, the handshake at the start of communication.

First, in step Sl, the sending side (host computer) sends a communication start signal (ENQ signal:
The ASCI I code is 05H).

In step S2, after sending out the ENQ signal, the timer T
Start l. This timer T1 sets a reception permissible period for an ACK signal transmitted from the receiving side (terminal device).

In step S3, it is checked whether an ACK signal (06H in ASCII) is obtained via the R++n line.

If no ACK signal is detected yet, step S6
At , it is checked whether timer T1 is in operation. At this time, if the time counting operation of the timer TI has already stopped, the process moves to step S7.

Thus, during the period defined by timer TI, A
Hiyama of CK signal is performed. When the ACK signal is received, in step S4, a certain amount of transmission data (for example, 80 bytes of data) is sent to the TxI line.
Send out.

Thereafter, if it is necessary to further transfer data, the handshake shown in steps S1 to S4 described above is repeated.

If the timer T1 finishes counting without receiving an ACK signal (step S6), a predetermined message signal (a signal requesting the receiving side to send some kind of response message) is sent in step S7. Send.

As this message signal, a prompt such as "I, 0GIN" is sent to the receiving side, and this 'LOG
The terminal that received “IN” will send the XON code (IIH)
A transmission request is made by sending this to the sending side.

Next, in step S8, timer T2 is started. This timer T2 is used to set the acceptable period for receiving reply messages sent back from the receiving side (terminal device).

In step S9, it is checked whether a reply message has been obtained from the receiving side. This message check is continued until the timer T2 finishes counting (step 5lO).

If no message is received from the receiving side even after the timing operation of timer T2 ends, data transfer is stopped.

On the other hand, when a reply message is received from the receiving side,
The handshake in steps S1 to S3 above (i.e. E
It is assumed that only the NQ-ACK handshake (NQ-ACK handshake) has not worked, and data in a predetermined data field (for example, 80 bytes of data) is transmitted in step Sll. At this time, until the data transfer is completed (step 512)
, 1 - The ENQ-ACK handshake described above is not performed.

Note that -1- If data transfer (X) is performed without executing the ENQ-ACK handshake described above, a message indicating this (an error has occurred on the terminal side, for example) will be displayed on the transmitting side panel. It is also possible to display "IACKERROR").

〔Effect of the invention〕

As described above, according to the present invention, the state of the communication partner is checked in two stages, so the receiving state of the communication partner can be quickly determined without requiring extra time. It is possible to decide whether or not communication is possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of a communication device to which the present invention is applied, Fig. 2 is an overall configuration diagram of a data communication system to which the invention is applied, and Fig. 3 shows the configuration of Fig. 2 in more detail. FIG. 4 is a flowchart showing the operation of this embodiment. IC...Medium host I/computer, SI...serial interface, TA, TB, T
C...Terminal equipment. Figure 1 Figure 2 (22ni222no Figure 4

Claims (1)

[Claims] 1) If a reception ready signal cannot be received from the communication partner within the first waiting time after sending a transmission start signal that is sent before a data signal, a predetermined message signal is sent, and a second 1. A communication control system, characterized in that when a response signal to the message signal is received within a standby time, transmission of the data signal is started.