JPH07264263A - Serial communication interface device - Google Patents

Abstract

PURPOSE:To provide a interface device automatically identifying a communication parameter with a minimum configuration receiving serial data. CONSTITUTION:The interface device is a start-stop serial communication interface device used to send/receive data to/from a computer and provided with a serial data receiver 1 waiting the equipment by a specific communication parameter, a means 2 identifying a transmission speed of the received communication parameter based on unit data received in the standby state, and a means 2 sampling the received serial data depending on a communication speed identified, comparing the data with a serial data pattern to identify a unit data length and a bit error detection method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial communication interface device for automatically detecting communication parameters when performing an asynchronous serial communication with a host computer via an RS-232C interface or the like.

[0002]

2. Description of the Related Art When performing serial communication with a host computer, it is necessary to match the communication parameters (communication speed (transmission speed)), unit data length, and bit error detection method. Conventionally, as a means for automatically detecting these communication parameters, the effective period of the start bit is measured and the communication speed is detected at the time interval.

[0003]

However, in the conventional communication parameter detecting device of this kind, in order to measure the effective period of the start bit as described above, a dedicated sampling pulse generator, a measuring counter and a timing are provided. There is a drawback that the system configuration becomes complicated because it requires a control circuit and the like.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide an apparatus capable of automatically identifying communication parameters with a minimum configuration for receiving serial data. To do.

[0005]

SUMMARY OF THE INVENTION The present invention is an asynchronous serial communication interface device for exchanging data with a computer, the serial data receiving device standing by for reception with specific communication parameters, and a unit for standby reception. A means for identifying the transmission rate of the communication parameter received based on the data, and sampling the received serial data according to the identified communication rate and comparing the data with the serial data pattern to detect the unit data length and bit error Means for identifying the method.

[0006]

[Operation] By waiting with a specific communication parameter,
The communication speed is detected from the reception result and the reception data.
By comparing the transmitted data patterns after speed identification, communication parameters such as unit data length can be identified.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the basic configuration of the present invention, and FIG. 2 is a timing diagram showing the types of AT command data.

In the figure, 1 is a serial data receiver,
Reference numeral 2 is a control circuit including a CPU for detecting communication parameters, and 3 is a serial reception signal line from the outside in the serial communication interface, which is connected to the serial receiver 1 and the control circuit 2, respectively.

The serial communication interface device of the present invention is applied to a device in which a command is transmitted from a host computer according to specific communication parameters.
When sending and receiving serial signals via the RS-232C interface with the host computer, normally A
The T command is used. As shown in FIG. 2, the AT command data has a data length of 7 or 8 bits and three types of parity (P) for error control: non, odd, and even. The data array is determined by the type of. Figure 2
In Pn, parity (P) is non, Po is parity (P) odd, and Pe is parity (P) even.
Indicates. And, for example, the description of 7 / Pn indicates that the data length is 7 bits and the parity (P) is non.

In this embodiment, the communication speed is 1
9200bps, 9600bps, 4800bps, 2
Communication is performed at four speeds of 400 bps.

Next, a method for detecting communication parameters according to the present invention when communication is performed based on the AT command will be described.

First, the control circuit 2 receives the communication parameter so that the serial data receiver 1 receives the specific communication parameter in response to the arbitrary communication parameter of the AT command while waiting for reception. To set. In this embodiment, the highest communication speed is 19200 bps, the data length is 7 bits, and the parity is n.
The serial data receiver 1 is set so as to wait on (Pn).

When a specific code signal is input from the serial data reception signal line 3, the serial data receiver 1 receives one unit data ('A') at a sampling clock when receiving data at 19200 bps set by the control circuit 2. ) To receive. The serial data receiver 1 takes in the code signal input from the reception signal line 3 by the sampling clock and gives the reception result and the hexadecimal data signal to the control circuit 2.

In the AT command, start (S
Since the TART) bit is defined as "0" and the stop (STOP) bit is defined as "1", if the sampled data is the above defined bit, "normal reception", other than the specified Is "frame error"
The serial data receiver 1 gives the reception result to the control circuit 2.

The communication speed and sampling mode of the received data are shown in the lower part of FIG. As can be seen from FIG. 2, depending on the communication speed at which the data is sent in the first unit, that is, the first byte, it is transmitted depending on the received data and "normal reception" or "frame error". Communication speed is uniquely determined.

For example, the received data is "00" in hexadecimal.
If h ”and the reception result is“ normal reception ”, the communication speed is 2400 bps.

Table 1 shows the relationship of the communication speed based on the received data sampled and the reception result.

[0018]

[Table 1]

When the received data is "41h", the communication speed is 19200 bps, and during normal reception (1 in the table), the data length is 7 bits and the parity (P) is set.
Is non or odd, and "frame error" (2 in the table) is when the data is other than the above.

The control circuit 2 stores the contents of Table 1 in a ROM or the like, and when the serial data receiver 1 receives the reception data (hexadecimal) of one unit data and the reception result,
The communication speed is detected according to the contents of the above table.

The control circuit 2 determines the sampling interval of the serial data receiver 1 and the control circuit 2 so as to receive the serial communication according to the detected speed, and after the serial data receiver 1 finishes receiving one unit of data. The signal transmitted to the serial data reception signal line 3 is sampled at the sampling interval.

Further, the ROM of the control circuit 2 stores the data pattern of the AT command data shown in FIG. The operation unit data length and the operation bit error detection method are determined by comparing the sampled data with the data pattern stored in the ROM. The control circuit 2 uses the determined operation communication parameters as the serial data receiver 1
By setting to, serial reception will be performed thereafter with the regular communication parameters.

Next, the detection of the operating speed will be further described based on the specific examples of FIGS. 3 and 4. In the case shown in FIG. 4, the host computer has a communication speed of 2400 bp.
s, data length is 7 bits, and parity is Pn. The serial data receiver 1 stands by at the highest communication speed of 19200 bps, the data length of 7 bits, and the parity of non (Pn).

As shown in FIG. 4, when data transmitted at 2400 bps is sampled by a sampling clock corresponding to 19200 bps, the sampled data has a truth value as shown in FIG. 4 (b). And the start bit is "0" and the stop bit is "
1 "and it is determined that the frame is a normal frame. Since the data used by the device or the like is in the reverse order of the transmission data, the bits are rearranged as shown in FIG. Since the basic data length in the standby state is 7-bit data, bit (bit) 7 is set to "
It is regarded as 0 ". This binary code is 16
When expressed in radix, it becomes "00h". As a result, the received data is "00h" and "normal reception" indicates that serial data receiver
The data is sent from the control circuit 2 to the control circuit 2.

FIG. 5 shows the case where the host computer transmits at a communication speed of 4800 bps, data of 7 bits, and parity Pn. Serial data receiver 1
Stands for 19200 bps, the data length is 7 bits, and the parity is non (Pn) as in the above.

As shown in FIG. 5, when the data transmitted at 4800 bps is sampled by the sampling clock corresponding to 19200 bps, the sampled data has a truth value as shown in FIG. 5 (b). And the start bit is "0" and the stop bit is "
It becomes 0 "and is judged as" frame error ". Then, the bits are rearranged as shown in FIG. 5 (c), bit 7 is regarded as" 0 ", and this binary code is hexadecimal. In this case, "78h" is obtained. As a result, the received data is "78h" and a "frame error" is sent from the serial data receiver 1 to the control circuit 2.

In this way, the communication speed can be detected based on whether the received data and the reception result are "normal reception" or "frame error".

After detecting the communication speed, the data inputted to the signal line 3 is sampled by the sampling clock corresponding to the communication speed and compared with the bit array shown in "T" of FIG. Determine the operating bit error detection method.

In the above-described embodiment, the specific communication parameters for waiting in the serial data receiver 1 are 19200 bps, which has the fastest communication speed, 7 bits of data length, and non (Pn) of parity. Not limited to this, other communication parameters may be used. When other communication parameters are used, it is necessary to input the corresponding received data and the relationship of the communication speed according to the received result into the ROM of the control circuit 2.

[0030]

As described above, according to the present invention, it is possible to automatically identify the communication parameters when the asynchronous serial communication is performed with the minimum configuration for performing serial reception.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a timing chart showing types of AT command data.

FIG. 3 is a diagram showing a sampling mode of the serial data receiver of the present invention.

FIG. 4 is a diagram showing a sampling mode of the serial data receiver of the present invention.

[Explanation of symbols]

 1 Serial data receiver 2 Control circuit 3 Signal line

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Claims (1)

[Claims] 1. A start-stop synchronous serial communication interface device for exchanging data with a computer, comprising serial data receiving means for waiting for reception with specific communication parameters, and communication parameters received on the basis of unit data received by standby. And a unit for identifying the unit data length and the bit error detection method by sampling the received serial data according to the identified communication speed and comparing the data with the serial data pattern. Serial communication interface device.