JPH0728297B2 - Data link system - Google Patents

Description

The present invention relates to a data link system in which a master station, which is a programmable controller, and a predetermined number of slave stations are linked together.

[Conventional technology]

FIG. 4 shows a data link system in which a master station and a slave station form a link. The remote stations No. 1 and No. 3 as slave stations handle bit data to be input / output by an input / output card. In addition, the remote station No. 2 has a screen and handles byte data such as screen display.

FIG. 5 shows the HDLC frame format of the high-level data link control loop means generally used in the above data link system.
The sequence synchronizes the frames by hardware, and the address of the slave station is designated by 8 bits of the address part. The control part represents various control information, and the information part has a text having an arbitrary bit length. The frame check sequence is a redundant part for error control.

Next, the operation will be described. According to the flag sequence of FIG. 5, the slave station receives the transmission frame in hardware synchronization and if the frame is sent to its own station by the address part, various controls are performed according to the contents of the control part and the information part. In addition, when the data link system between the master station and the slave station is configured, the data transfer between the master station and the slave station is performed with respect to the remote station No. 1,
Data transfer to all slave stations is performed by using the address part shown in Fig. 5 as a global address for all stations at once, rather than performing it for Unit 2 and then for Unit 3. Is done at high speed.

However, as shown in Fig. 5, the remote station Nos. 1 and 3 treat the data as bit information such as ON / OFF information exchanged with the external device, and the remote station No. 2 exchanges the data with the external device. When processing information of different times, such as handling as byte information such as numerical information exchanged between data, whether the data is bit information or byte information in the information part of FIG. A flag is provided to determine whether there is any information, and it is determined whether the information matches the type of the own station. If the information matches, the data is received, and if it does not match, the information is ignored.

[Problems to be Solved by the Invention]

The transmission frame of the conventional programmable controller that has the function of configuring a link is designed to receive the transmission frame in synchronization with the flag sequence. Therefore, for example, only one frame format, such as HDLC, can be used. Data link could not be performed. Therefore, as shown in FIG. 4, when slave stations that handle different types of information are mixed, all slave stations must send and receive data by using the address part as a global address. There is a problem in that it is burdensome and takes a lot of processing time in the slave station system.

The present invention has been made to solve the above problems, and in a data link system in which slave stations handling different types of information are mixed, a data link in which the processing time between slave station systems is shortened. Aim to get the system.

[Means for Solving the Problems]

In the data link system according to the present invention, a master station, which is a programmable controller, and a predetermined number of slave stations are link-connected, and transmission frames having different types of information such as a transmission frame handling bit information and a transmission frame handling byte information are described above. In the data link system transmitted from the master station to the slave station, the transmission frame is configured so that a synchronization flag having a predetermined number of bits for receiving synchronization is headed, and the synchronization flag is information indicating the type of information to be handled. The slave station has a shift register into which received data is shifted in, and the bit pattern of the synchronization flag indicating that the type of information handled is the type handled by the local station is shifted in to the shift register. Has a logic circuit that determines whether or not there is a synchronization based on the determination output of the logic circuit. It is those in which to choose receiving the transmission frame.

[Action]

In the data link system according to the present invention, a master station, which is a programmable controller, and a predetermined number of slave stations are link-connected, and transmission frames that handle different types of information such as a transmission frame that handles bit information and a transmission frame that handles byte information are master stations. In a data link system transmitted from a mobile station to a slave station, the transmission frame is configured to start with a synchronization flag consisting of a predetermined number of bits for receiving synchronization, and the synchronization flag has information indicating the type of information to be handled. The station has a shift register into which received data is shifted in, and a logic that determines whether or not the bit pattern of the synchronization flag indicating that the type of information to be handled is the type handled by the local station is shifted into the shift register. It has a circuit, and it synchronizes based on the judgment output of the logic circuit and selectively receives the transmission frame. .

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIGS. 2A and 2B show an example of a transmission frame having a synchronization flag at the head for synchronization, and FIGS.
(B) is a shift register (1) and AND circuits (2a), (2
b) and, which show selective reception means on the slave station side for detecting the synchronization flag.

In FIG. 1, the synchronization flag is set to 111101 for the transmission frame of pattern A shown in FIG. 1A, and the synchronization flag is set to 111110 for the transmission frame of pattern B shown in FIG.
To transmit to the child station side. On the other hand, the slave station system which receives the transmission frame of the pattern A receives the transmission frame A by synchronizing with the transmission frame A of FIG. 1 by the circuit shown in FIG. The slave station system for receiving the transmission frame B receives the transmission frame B in synchronization with the transmission frame B of FIG. 1 by the circuit shown in FIG.

For example, in Fig. 4, the remote station Nos. 1 and 3 are
The transmission frame A of the pattern A shown in FIG. 1 (a) is linked with the master station as a unit for handling bit information, and the remote station 2 receives the transmission frame B of the pattern B shown in FIG. 1 (b). Link with the master station to handle byte information.

That is, the synchronization flag has information indicating the type of information to be handled, and the bit pattern of the synchronization flag indicating that the type of information to be handled is the type handled by the local station is shifted into the shift register (1). On the condition that the transmission frame is synchronized, the transmission frame is received. The shift register (1) is configured so that the received data is shifted in.

It should be noted that by adding the flip-flop (3) and the exclusive OR circuit (4) to the selective receiving circuit of the second illustrated configuration example of the slave station system to configure the synchronization flag pattern setting circuit of FIG. Depending on the station, it is possible to assign a synchronization flag to each slave station system. For example, when the power of the data link system is turned on, all the slave station systems set the synchronization flag to 11 in the pattern A shown in FIG.
1101, and in the transmission frame A, the master station transmits the bit pattern of the synchronization flag to each slave station system as initial communication. The slave station system which received it receives the bit pattern of the sent synchronization flag as the third
By writing to the flip-flop (3) in the figure,
The synchronization signal for frame synchronization can be changed.
After the above initial communication is completed, the data link between the master station and the slave station can be performed.

It should be noted that in FIGS. 1 and 2 above, the patterns A, B and 2
Although the types of transmission frames have been described, since the synchronization flag in FIG. 1 has 6 bits, (2 ⁶ -1) types of patterns are possible. Further, by increasing the number of bits of the synchronization flag, the types of patterns of the synchronization flag will increase.

[Effects of the Invention] As described above, according to the present invention, data transmitted from a master station to a slave station is a transmission frame in which different types of information are handled, such as a transmission frame handling bit information and a transmission frame handling byte information. In a link system, a transmission frame is configured so that a synchronization flag having a predetermined number of bits for receiving synchronization is placed at the head, the synchronization flag has information indicating the type of information to be handled, and the slave station is shifted in the received data. And a logic circuit for determining whether or not the bit pattern of the synchronization flag indicating that the type of information handled is the type handled by the local station is shifted in the shift register. The transmission frame is synchronized based on the judgment output, and the transmission frame is selected and received. Only the selected data can be selectively received, the subsequent reception processing in the slave station is speeded up, and the processing of the entire data link system can be speeded up.

[Brief description of drawings]

1 (a) and 1 (b) are explanatory views of a transmission frame of the present invention and an example of a synchronization flag for synchronizing the transmission frame, and FIGS. 2 (a), 2 (b) and 3 detect the synchronization flag. FIG. 5 is a circuit diagram showing an example of selective receiving means to be performed, FIG. 5 is a transmission frame format diagram of HDLC, and FIG. 4 is a configuration diagram of a data link system. (1), (2a) and (2b) are a shift register and an AND circuit which constitute selective receiving means. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A master station, which is a programmable controller, and a predetermined number of slave stations are link-connected, and transmission frames having different types of information such as a transmission frame handling bit information and a transmission frame handling byte information are transmitted from the master station. In the data link system transmitted to the slave station, the transmission frame is configured to start with a synchronization flag consisting of a predetermined number of bits for receiving synchronization, and the synchronization flag has information indicating the type of information to be handled, The slave station has a shift register into which received data is shifted in, and whether or not the bit pattern of the synchronization flag indicating that the type of information handled is the type handled by the local station is shifted in to the shift register. Has a logic circuit that determines whether or not the transmission frame is selected based on the determination output of the logic circuit. A data link system characterized by selective reception.