JP3208930B2 - Intelligent modem - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem for a public line, and more particularly to an intelligent modem controlled by an AT command.

[0002]

2. Description of the Related Art Various communication controls such as automatic transmission and automatic reception are enabled by sending a command from a data terminal equipment (hereinafter referred to as DTE) such as a personal computer. An intelligent modem with an automatic identification function has been widely used recently. One of the command systems for controlling this kind of intelligent modem is an AT command. The AT command is also called a haze command, and automatically recognizes a communication speed [bps] between the DTE and the modem and a character format (data bit length, presence / absence of parity, etc., the same applies hereinafter). It is possible to communicate without using it, and it is currently used most frequently.

[0003]

However, although the AT command is convenient as described above, it has various operational problems. For example, in a communication system as shown in FIG.
The modems are connected to each other by a communication line,
30, when transmitting data to the attended DTE 33 having an operator through the modems 31, 32, the modem carrier on the communication line is interrupted due to noise mixed in the communication line or erroneous operation of the operator. It is assumed that 31 has determined that the carrier has been disconnected. At this time, the modem 31 enters a command mode in which the communication line is released (on-hook) and a command from the DTE 30 is awaited. However, on the DTE 30 side,
Since it takes a predetermined time to stop the data currently being transmitted, various data are being sent to the modem 31 during this time.

[0004] In the AT command system, the modem automatically recognizes the DTE communication speed and character format using AT to CR (line feed) codes. Therefore, if
If there is a code that can be read as "A" in some data rate or character format in the data transmitted by the DTE 30 instead of as a command, the modem 31
The side continues to wait for the upcoming "T" and "CR" at its baud rate and character format.

For example, 9600 [bps], 8 bits,
During communication without parity, 300 [bps],
When a code that can be read as "A" with 7 bits and odd parity arrives, the modem 31 waits forever until a code that can be read as "T" or "CR" is received at the same communication speed and character format. Since the DTE 30 cannot even know that fact,
A command is transmitted under the initial condition of 9600 [bps], 8 bits, and no parity. However, this command does not function at all because of the waiting state, and there is a problem that the communication system is substantially down.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an intelligence modem which drastically reduces the possibility of substantial system down when a carrier on a communication line is disconnected. It is in.

[0007]

According to a first aspect of the present invention, a communication speed and a character format with a DTE are automatically recognized by an AT command and a carrier disconnection on a communication line is detected. Sometimes, in the intelligence modem which releases the communication line and shifts to a command mode waiting for a command input from the DTE in the communication speed and the character format, the automatic recognition process is prohibited and the communication speed and the character format are predetermined. An interface fixing means for fixing the object is provided.

[0008] A second invention for achieving the above object is:
Performs automatic recognition of the communication speed and character format with the DTE by the AT command, and releases the communication line when a carrier disconnection on the communication line is detected, thereby opening the DTE with the communication speed and character format.
An intelligent modem which shifts to a command mode for waiting for a command input from the mobile terminal is provided with a timer for delaying a time from detecting the carrier disconnection to shifting to the command mode.

[0009] In the first or second invention,
An initializing means for initializing the internally held information including the communication speed and the character format according to an initialization command signal sent from the DTE may be added.

[0010]

In the intelligent modem according to the first aspect of the present invention, automatic recognition processing of the communication speed and character format performed using the AT to CR (line feed) code of the AT command is prohibited by the interface fixing means. Fix to the determined communication speed and character format. As a result, even if a code that can be read as "A" in any communication speed or character format exists in the data transmitted by the DTE, not as a command, "T" and "CR" come at that communication speed. Can be immediately executed without waiting for the command from the DTE.

[0011] In the intelligent modem according to the second invention, the time from when the carrier disconnection on the communication line is detected to when the command mode is entered is set by a timer, and after the set time has elapsed, a command from the DTE is accepted. Therefore, even if the carrier disconnection on the communication line is detected, the mode does not immediately shift to the command mode.
The probability of recognizing the code of “A” of the T command is reduced, and the situation of waiting for the subsequent “T” or “CR” is avoided.

By initializing the internally held information by the initialization means, the state becomes exactly the same as after power-on, and the cause of the function stop in the command mode is eliminated.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a connection configuration diagram of one embodiment of the present invention, in which 10 is an intelligent modem, 11 is an interface setting unit, 12 is a setting information reading unit, 13 is a memory,
Reference numeral 14 denotes a timer, 15 denotes an initialization processing unit, and 16 denotes an intelligent processing unit. Reference numeral 20 denotes a DTE, which is connected to the intelligent modem 10 via a transmission cable. Further, the intelligent modem 10 is connected to another intelligent modem (not shown) via a communication line.
Is connected to

The interface setting section 11 sets selection / prohibition of a communication speed and a character format automatic recognition process with the DTE 20 by an AT command. Specifically, a DIP-SW (dip switch) of the modem main body is set. : Not shown) is assigned to this function.

The setting information recognizing unit 12 reads the setting information of the interface setting unit 11 in response to the internal reset process, and determines the communication environment according to the setting state of the selection / prohibition of the automatic recognition processing of the AT command. is there.
This is, specifically, a gate IC composed of an EEPROM.
(Integrated circuit) or a parallel input / output LSI (large-scale integrated circuit) is connected to the DIP-SW to convert each setting information into a digital signal, and these signals are guided to the CPU via an internal bus or the like. For example, when the prohibition of the automatic recognition process is set, at least the communication speed and character format information guided to the command execution unit 16 are fixed to those read from the memory 13. Thereby, the subsequent communication with the DTE 20 is performed at the fixed communication speed or the like.

The intelligent processing unit 16 reads out the recognized communication speed and character format when the automatic recognition processing of the AT command is selected, and reads out the data from the memory 13 when the automatic recognition processing is prohibited. DT based on communication speed and character format
The command sent from E20 is executed, and normal intelligent processing is performed.

The timer 14 is used to set a time for releasing the communication line and returning to the command mode when detecting a carrier disconnection or the like. The setting time can be arbitrarily selected from two meanings: a time from simply switching the carrier to the command mode and a time when there is no data or the like input from the DTE 20 after the carrier is cut.

The initialization processing unit 15 includes a DTE 20
The internal holding information including the communication speed and the character format is initialized (reset) by an initialization command signal sent from the device, for example, “ER signal off” of RS232C.

Next, the initial operation of the intelligent modem 10 having the above configuration will be described with reference to the processing procedure diagram of FIG.

The setting information recognizing section 12 reads the setting information of the interface setting section 11, that is, the setting state of the DIP-SW (S (step, the same applies hereinafter)) 20 upon the internal reset processing due to the modem power-on or the modem reset.
1). Next, it is determined whether or not the automatic recognition processing is prohibited based on the read setting information (S202). If the processing is prohibited, the subsequent automatic recognition processing is stopped and the communication speed and the character format are changed. Memory 1
3 (S203). Then, an initialization process is performed (S204), and then a normal intelligent modem process is performed (S20).
5). If the automatic recognition process is not prohibited, the initialization process is directly performed (S204).

In the normal operation state after such an initial operation, when the disconnection of the carrier on the communication line is detected, the communication line is released and the timer 14 is started. Then, after the set time of the timer 14 has elapsed, the communication speed and the character format are read from the memory 13 and the mode shifts to the command mode. As a result, after the communication line is released, the DTE
In the data that 20 sent, not as a command,
Even if there is a code that can be read as "A" at any communication speed or character format, the following "T" or "CR"
, And the possibility of the communication system going down is drastically reduced as compared with the related art.

The prohibition of the automatic recognition process and the delay of the transition time to the command mode by the timer 14 may be used in combination or may be used selectively.

Even in the event that the communication system goes down, the initialization processing unit 15 is started by turning off the RS232C ER signal (data terminal ready signal) from the DTE 20 to retain the internal data including the communication speed and character format. The information is completely initialized, and each processing shown in FIG. 2 is executed again. As a result, the cause of the function stop in the command mode is removed, and the normal operation of the communication system becomes possible.

As described above, according to the intelligent modem of the present embodiment, the possibility of substantial system down after opening the communication line is significantly reduced, and the conventional problems can be solved. The present invention is not limited to the above-described embodiment, and the configuration can be arbitrarily changed without departing from the gist of the invention.

[0026]

As is apparent from the above description, the intelligent modem of the present invention has an interface fixing means for inhibiting the automatic recognition processing of the communication speed and the like by the AT command and fixing the processing to a predetermined one. In addition, there is an effect that it is possible to avoid a substantial stoppage of the command mode when the carrier on the communication line is disconnected.

The intelligent modem according to the present invention has a timer for delaying the time from the detection of the carrier disconnection to the transition to the command mode, and the operation is stopped in an unstable state immediately after the carrier disconnection. This has the effect of stabilizing the operation after the transition to the command mode.

Further, DT is added to the intelligent modem.
By adding initialization means for initializing the internally held information including the communication speed and the character format according to the initialization command signal sent from E, the cause of the function stop in the command mode is removed, and the normal operation of the communication system is improved. Will be possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of an intelligent modem according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an initial operation of the intelligent modem according to the embodiment.

FIG. 3 is an operation explanatory diagram of a communication system including a conventional intelligent modem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Intelligent modem 11 ... Interface setting part 12 ... Setting information recognition part 13 ... Memory 14 ... Timer 15 ... Initialization processing part 16 ... Command execution part

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Claims (3)

(57) [Claims] The present invention performs automatic recognition processing of a communication speed and a character format with a data terminal device using an AT command, and releases a communication line when a carrier disconnection on the communication line is detected to detect the communication speed and the character speed. An intelligence modem which shifts to a command mode for waiting for a command input from the data terminal device in a character format, comprising interface fixing means for inhibiting the automatic recognition process and fixing the communication speed and the character format to predetermined ones. Intelligent modem. 2. An automatic recognition process for a communication speed and a character format with a data terminal device by an AT command, and when a carrier disconnection on a communication line is detected, the communication line is opened to release the communication speed and character format. An intelligence modem for transitioning to a command mode for waiting for a command input from the data terminal device in a character format, comprising a timer for delaying a time until the transition to the command mode after detecting the carrier disconnection. Intelligent modem. 3. The intelligent modem according to claim 1, further comprising initialization means for initializing the internally held information including the communication speed and the character format in accordance with an initialization command signal sent from the data terminal device. An intelligent modem, characterized in that: