JPH0516777B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a response method for broadcast communication in a data transmission system in which a plurality of data transmission control devices (stations) are connected to a loop-shaped common transmission path. [Prior Art] In broadcast communication, one message is simultaneously transmitted to a plurality of receiving stations in a system, but generally the receiving stations are an unspecified number depending on the system. Therefore, it is impossible for the transmitting side to confirm the status of the receiving side, that is, the reception buffer busy status of the receiving station, by sequentially receiving responses from each receiving station. For this reason, if there is a buffer-busy receiving station during broadcast communication, the message of the broadcast communication may not be received at that station. In contrast, conventionally, as described in Japanese Patent Application Laid-Open No. 59-6543, a response method was used in which the response from each receiving station was passed on to the adjacent receiving station, and the response was sent as one response to the source station. . [Problems to be Solved by the Invention] The conventional response method described above has a problem in that a response cannot be sent when all receiving stations are abnormal. An object of the present invention is to enable the transmitting station to correctly and reliably notify the transmitting station whether all of the receiving stations are ready for reception, without having to recognize the number of receiving stations on the loop transmission path. To provide a response method for broadcast communication. [Means for solving the problem] The purpose of the above is to create an address recognition field in which each receiving station that receives a transmission frame writes whether or not it recognizes that the destination address in the frame is itself; This is achieved by providing a buffer field in the transmission frame that writes whether or not the reception buffer of Ru. [Operation] The transmitting station transmits the destination address in the transmitting frame to all stations (indicating broadcast communication).
Send address recognition field as unrecognized and buffer field as busy. When this is sent sequentially to each receiving station, each receiving station determines that the destination address indicates its own station as the receiving station, or when the address recognition field in the frame that is sent indicates that it is already the receiving station. If the station is set to the receive value indicating that the station has received the received station, the address recognition field is set to the receive value, and if the station determines that the station is the receive station and the receive buffer is ready (receivable state), If the address recognition field in the transmitted frame is the received value and the buffer field indicates buffer busy, the buffer field is set to busy, otherwise the buffer field is set to ready and the next Send the frame to the station. As a result, when a frame that has gone through the loop returns to the transmitting station, if the address recognition field in that frame is a received value, it is known that at least one station has determined that it is the receiving station.
If the buffer field is ready, it means that all receiving stations have received the information. Also, if the buffer field is busy, it means that at least one receiving station was busy and could not receive data. [Example] Hereinafter, an example of the present invention will be described based on the drawings. FIG. 2 shows a configuration example of a loop-type data transmission system to which the present invention is applied, in which stations ST1 to ST6 are connected to a loop-shaped transmission path 2. In FIG. FIG. 3 shows the frame structure of the HDLC format used for sending and receiving messages between stations on the transmission line 2. In the figure, F is a flag, a unique 8-bit code indicating the start and end of a frame,
DA is the destination station address, which indicates the address of the destination station. C indicates a control command, which is used for various controls. SA is the source station address, which indicates the address of the station that sent the message. DATA is
Indicates message information. FCS is an error checking pattern for frames of message information, and if there is an error, the frame is discarded. In addition, the present invention provides two fields, AR and BUF. AR is an information area that indicates whether or not the frame is recognized as being addressed to itself, and BUF is an information area that indicates whether or not the receiving buffer is in a processing waiting state. This is an information area that shows the FIG. 4 shows an example of the configuration of one station, in which the received signal from the transmission line 2 is demodulated and reproduced through the receiver 3, inputted to the HDLC control circuit 5,
Constructed as a received frame. The same circuit 5 also determines whether the frame format data configured by the HDLC control circuit 5 is destined for this station.
At that time, it is also determined whether the reception buffer is busy or not, and the determination results C and D are sent to the reception state control circuit 9. The results of the AR and BVF fields in the received frame are also taken out and sent as signals A and B to the reception state control circuit 9. When it is determined that the station is a receiving station, the received data is stored in the buffer area of RAM 8 via bus 11, and then HDLC control circuit 5
When it receives up to the end flag F of the HDLC frame, it notifies the microprocessor 6 by turning on the interrupt signal 10. Furthermore, the demodulated reproduced data is sent out to the transmission line 2 through the modulator 4 and sent to the next station. Furthermore, when the frame is not addressed to this station, data is not stored in the reception buffer area in RAM8. The ROM 7 is a memory in which a microprogram for controlling the station by the microprocessor 6 is stored. FIG. 1 shows an embodiment of the reception state control circuit 9, which is a feature of the present invention, and is composed of gates 91-95. This circuit uses the contents A and B of the AR and BVF fields in the received frame and the judgment results C and D in the HDLC circuit 5 of its own station to send the AR and BVF fields in the transmitted frame to the next station.
This circuit determines the contents E and F of the BVF field, and its truth table is shown in Table 1.

〔Effect of the invention〕

According to the present invention, the status of the receiving side can be notified to the transmitting side regardless of the number of stations, which has the effect of facilitating the expansion of a transmission system that performs broadcast communication. Since this can be done simultaneously with transmission, it also has the effect of improving communication processing speed.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of a reception state control circuit which is a feature of the present invention, Fig. 2 is a diagram showing an example of a loop transmission system, Fig. 3 is a configuration diagram of an HDLC format frame, and Fig. 4 is a diagram showing a station. FIGS. 5 and 6 are explanatory diagrams of the operation of the circuit shown in FIG. 1. 2...Loop transmission line, 5...HDLC control circuit,
9... Reception state control circuit, 91, 92... OR gate, 93-95... AND gate, AR... Address recognition field, BVF... Buffer field.

Claims (1)

[Claims] 1. In a response method for broadcast communication in a data transmission system in which a plurality of stations are connected in a loop, first and second fields for responses are provided in the transmission frame, and each station has the above-mentioned fields. In addition to providing reception status control means to replace the first and second fields, the transmitting station sets the first field to an unreceived value, the second field to a busy value, and the destination address to all stations indicating broadcast communication. In each receiving station that transmits a transmission frame with an address and sequentially receives the transmission frame, the reception state control means provided in the station controls whether the received transmission frame is addressed to the own station or the address in the received transmission frame. When the first field is a received value, the first field in the transmitted transmission frame is set to the received value, otherwise it is set to an unreceived value, and the first and second fields in the received transmission frame are set to the unreceived value. and a busy value or a received value and a ready value, and when the received transmission frame is addressed to the local station and the receiving buffer of the local station is in a ready state where it can receive, the second field in the transmitted transmission frame is set to the ready value; If not, it is set to a busy value, and thus the first and second fields are processed sequentially at each receiving station and the transmitting station receives the completed transmission frame to check whether all receiving stations have received the information. 1. A response method for broadcast communication, characterized by determining whether