JPH0417579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a data transmission device, and particularly to a data transmission method used for data transmission between two or more computers or terminal devices including the same.

(Prior art) Conventionally, this type of data transmission method was based on ISO or JIS.
Transmission codes shown in the following are used, and in cases where it is particularly necessary to increase transmission efficiency, transparent mode systems that can transmit binary images are also accepted.

But in this transparent mode,
If the same code as the DLE code happens to exist in the binary image data, a control code called DLE is prefixed and transmitted to distinguish it, and if there are two consecutive DLEs on the receiving side, the first one is
This method prevents the same pattern as the DLE+control code from occurring. This method requires a function on the receiving side to always monitor two consecutive characters, and in a data transmission method that reads the code by interrupting the received data for each character, Direct comparison control is not possible, and the program always compares and reads the two received characters, so the comparison program runs between the programs that read the characters, which causes characters to be dropped during high-speed transmission, leading to retransmission. Alternatively, when reducing the transmission speed from the beginning to save time, there was a problem in that even though the system was originally intended for high-speed transmission, it was not possible to do so.

(Object of the Invention) An object of the present invention is to provide a data transmission device using transparent transmission, which enables transmission control with only one character at the moment of reception, in order to eliminate the above-mentioned drawbacks.

(Structure of the Invention) In the data transmission method between systems separated at two or more points according to the present invention, there is provided a processor for editing data and controlling a protocol, and a memory for storing a program and data for operating this processor. , a communication control circuit that converts the data to be transmitted from serial to parallel, a bus that connects at least these three parts in a signal manner, and modulates and demodulates the input and output serial transmission signals from the communication control unit when the distance between the systems is large. It consists of a modulator and modulator, and on the transmitting side, a predetermined 1-byte delimiter code indicating the end of the data is added to the original data string of the binary image to be transmitted, and the delimiter code is extracted from the original data. means for editing and transmitting as one message a code string indicating the position of the previously removed code in the original data and a final code of 1 byte following the delimiter code by removing only the data of the code equal to the delimiter code; , a data transmission system is obtained which is characterized in that the receiving side has means for reassembling original data from each code included in this message.

(Principle of the Invention) Normally, both transmitting and receiving devices have the same configuration as described below, so only one of them will be described here. The central processor receives and analyzes interrupt signals when data arrives,
It reads and stores data, and also controls the contents of received data, errors, and non-response based on the protocol, and performs all necessary processing in conjunction with the memory connected to the bus.

If necessary, the line that actually transmits data is led to a communication control unit connected to this bus through a modulation/demodulation unit, so that serial signals on the line side and parallel signals on the bus side can be mutually converted. This communication control section is the most common type that provides one interrupt signal to the processor for each transmission/reception of one character.

Here, the transmission format used in the present invention will be explained. As mentioned above, the original data is a binary image, so make sure that the transmitted data does not contain a code with a predetermined bit format that indicates the end of the data to the receiving side and a similar code that indicates the end of the message. . Here, the former is OO (hexadecimal) and the latter is FF (16
The message length of the source data should be 254 characters or less. Remove the code (OO) that is equal to the code that indicates the end of data from the source data, fill in the space between them, place the data end code (OO) next to the final character of the source data, and then place the code (OO) that is equal to the code that indicates the end of data in the source data. Arrange the positions of the source data with the first character as O1 (hexadecimal) and the last character as FE (hexadecimal). Put the message end code (FF) at the end, and then
One message.

In this case, bits, characters, and synchronization characters for error control such as a validity bit may be added, but these are omitted here because they are not an essential problem of the present invention.

Effect In such a transmission format, if OO is found in the continuous reception character, it can be known that the data has ended with the code immediately before this, and the next character from the character after OO can be known. The character immediately before the discovered FF can be interpreted as indicating that the OO code that should have been in the data has been omitted, and immediately after receiving the FF, the program ends reception and performs the necessary protocol. I take control and begin restoring the original data according to my previous promise.

(Example) Next, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an embodiment of the present invention. Referring to FIG. Signals are exchanged. When systems are separated by distance,
Alternatively, if a lot of noise is generated on the line, the modulation/demodulation section 5 is connected to the communication control section 3. Therefore, the line 6 is connected to the modulation/demodulation section 5 or the communication control section 3.

In this case, there are no special specifications requirements for the processor 1, memory 2, and bus 4, as long as they are capable of normal interrupt processing. The modulation/demodulation unit 5 may also be compatible with the data transmission rate and synchronization method. The communication control unit 3 may use the most general interrupt method for each character. Overall, it is a very simple general computer system.

In FIG. 2, the character formats transmitted between the systems are shown, with a representing the original data and b representing the data on the transmission line.
That is, on the transmitting side, a is converted to b and transmitted, and on the receiving side, b is converted back to a. Both a and b are binary image data, and are very short typical examples. The atomic data in this example consists of seven characters, and if the position number of the first character is defined as O1, the position of the last character will be O7. Here the number of characters is 254 (FE)
Must be below. The reason is that if 255 (FF) exists in the character location information code, there is a risk that it will become indistinguishable from the message end code (FF). In example a, position 02,0
OO exists in 5,06. In example b, from a
Continuing the result of removing OO without a gap, position 01
After compression from 04 to 04, a data end code (00) follows in position 05, and a in positions 06 to 08.
Bit position 02 where 00 omitted in the example is placed,
05 and 06 are entered in order. Finally, a message end code FF is added to form one message.

The conversion between a and b is done through the program, but on the receiving side, finding 00 means the end of the data, and finding FF means the end of the message. It is sufficient to always monitor only one character being received at the time, and the program running time between each character can be kept to a minimum. In addition, in principle, as shown in Figure 2, the format length of the original data and the transmitted data is the former + 2 characters, so the redundancy is generally smaller than the DLE addition method specified by JIS, and both are transparent. This can meet the original purpose of high transmission efficiency.

(Effects of the Invention) The present invention provides the following advantages:
This has the effect of making it possible to control transmission using just the character.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Figures a and b show an example of the transmission format. 1...Processor, 2...Memory, 3...Communication control section, 4...Bus, 5...Modulation/demodulation section.

Claims (1)

[Claims] 1. In a data transmission method between systems that are separated and scattered at two or more points, there is a processor for editing data and controlling protocols, a memory for storing programs and data to operate this processor, and a memory for storing data to be transmitted. It consists of a communication control circuit that performs serial-to-parallel conversion, a bus that connects signals to at least these three parts, and a modem unit that modulates and demodulates input and output serial transmission signals from the communication control unit when the distance between the systems is large. On the side, a predetermined 1-byte delimiter code indicating the end of the data is added to the source data string of the binary image to be transmitted, and only the data with the same code as the delimiter code is removed from the source data. Following the delimiter code, a code string indicating the position of the previously removed code in the source data, followed by a 1-byte final code.
1. A data transmission system comprising means for editing and sending out a single message, and means for reassembling original data from each code included in the message on the receiving side.