JPS60201757A - Transmitter - Google Patents

Abstract

PURPOSE:To ensure the communication as a whole even in case the power supply is cut off in one of transmitters connected in series, by using a relay contact circuit which is closed and opened when the power supply is cut off and applied respectively as a by-pass of each transmitter. CONSTITUTION:Communication media 100a and 100b are connected to a circuit connection control part 301 consisting of a relay which is usually closed. Both communication media are connected to each other when the function of a node 300 is stopped in order to eliminate the effect of the node stoppage for a network system. When the node 300 is working, the part 301 separates both media 100a and 100b from each other and connects the node 300 in series to both communication media.

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a transmission device in a network system configured by connecting a plurality of transmission devices in series via a communication medium. [Prior Art] Conventionally, in a network system in which transmission devices are connected through a communication medium, if the power of one transmission device is cut off, the data to be transmitted is interrupted at that transmission device, and the data is transferred to the next transmission device. I couldn't send it. In order to avoid this problem, transmission devices cannot be connected in series via a communication medium, and can only be connected in a path. Therefore, when data is transmitted between certain transmission devices, other devices cannot transmit data at all, resulting in inefficiency. [Objective] The present invention has been made in view of the drawbacks of the prior art described above, and its purpose is to provide a transmission device that configures a network that does not affect other network component devices even when the transmission device is stopped. Our goal is to provide the following. EMBODIMENT OF THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram of a serial packet switching network system, which is a network system according to the present invention, in which 100 is a communication medium, and 101-105 are transmission devices (101-105) that perform transmission control and are connected in series via the communication medium 100. 110 to 113 represent terminals or servers (hereinafter referred to as hosts) connected to the node lot, and in this embodiment, up to four hosts can be connected to each node. The communication medium 100 between each node 1 is bidirectional, and packet communication is performed independently between the nodes. The packet frame configuration for this packet communication is
As shown in FIG. FIG. 2 is a diagram showing the packet frame structure used in this system, where 201 is a start flag for starting one frame, 202 is a destination address section of the frame, 203 is a source address section, and 204 is a transmission described later. This is a command that indicates control of a node's entry into the network, response as to whether received data is correct or incorrect, data communication control such as broadcast communication control, node status, etc. 205 is a data length designation section indicating the length of the transmission information field. 206 is a transmission information field having a maximum length of 256 bytes. 207 is a frame CRC check code for error control. Note that 208 is an end flag. The above-mentioned destination address section 202 and source address section 20
The details of 3 are shown in FIG. 2(B).The address part includes a node address 211 indicating the address of the node, a group address 212 indicating the address of the group to which the host connected to the node belongs, and an address within the group to which the host belongs. It consists of an intra-group address 213 indicating. Table 1 shows examples of this group name and group address. Here, an example is shown in which the groups are divided into hosts according to the R3-232C standard, hosts according to the GP-IB standard, printer servers, and file servers. Table 1 In addition to the data packet frames described above, there are polling control frames shown in 21st W (A) and selecting control frames shown in 2nd IJ (B) as control frames between nodes and hosts. The polling control frame consists of 'EOT' 221, polling codes 'POL' 222 and 'ENQ' 223, and the selecting control frame consists of 'EOT' 221 and selecting codes 'SEL'°224 and 'ENQ'.
223. The host polls and selects the nodes using this control frame, and sends and receives data. Next, the configuration of the nodes in this system will be explained with reference to the block diagram in Figure 4. The node 300 corresponds to the nodes 1.01-105 in FIG.
01, and this line connection control unit 301 controls to connect both communication bodies when the node 300 is stopped, and to disconnect both communication media when the node 300 is operating. For example, this line connection control section 30
Reference numeral 1 is a normally closed relay, which is configured to be connected indirectly when the power of the node 300 is turned on, so that both communication media 100a and 100b are connected to the power source of the node, and the node is connected as a network system. It is possible to perform control that is not affected by stoppage 2. A transmission circuit A304 is connected to the communication medium 100a via a transceiver A302, and a transmission circuit B505 is connected to the communication medium 100b via a transceiver B503.
The received packet data on the communication medium is sent to the control unit, and the transmitted packet data is sent onto the control communication medium. 306 is a node address setting section;
A network address of 00 is set. This node address is set so that the value becomes larger (or smaller) in order from the node connected to one end of the system to the node connected to the other end. In the example of FIG. 1, the node 101 has the node address (R0
1), node 102 (R08), node 103 (#
lO), node 104 is (R18), node 105 is (
R20) address setting. In this way, by setting the node address so that it increases in a certain direction, the mate can use the own node by simply comparing the send request address from the host and the own node address, without updating the memory of the network configuration on the mate. It is possible to determine the direction in which a packet is sent from, and to immediately determine whether a transfer request packet sent to the own node is a packet addressed to the sending direction node or not just by comparing it with the address of the own node. A control unit 310 controls the transmission circuit A 304 or the transmission circuit B 505 to perform packet exchange on the communication medium 100a or 1oob. -The power control unit 310 has a configuration for data communication with each connected host, and depending on the configuration of the transmission interface unit, a part that can be used with an R3232C standard host and a GP-IB standard host can be used. It is divided into different parts. Up to four hosts can be connected to the control unit 310, and a socket address setting unit (C(
321), D (331), E (341), F (35
1)) and transmission circuits (C(332), D(332)
), E (342), F (352)) and transmission interfaces (C (323), D) between each transmission circuit and the host.
(333). E (343), F (353)). Next, details of each transmission circuit section will be explained with reference to the block diagram of FIG. 5. 502 is a transceiver (corresponding to 302 and 303 in FIG. 4) in the case of transmission circuits A304 and B505, and transmission circuits C322 and D332. In the case of E342 and F352, it is an interface section corresponding to a transmission interface (corresponding to 323, 333, 343, and 353 in FIG. 4). Prior to frame reception, a carrier signal sent onto the communication medium is detected by the carrier detection unit 523 via the interface unit 502, and the receiving circuit 520 is placed in a receiving state. Further, received data etc. from the interface section 502 are inputted to a receiving circuit 520, and inputted frame data is transferred to a receiving buffer 521. At that time, only the address part in the received frame is stored in the address register 522, and the address data set in this address register 522 is passed to the comparator 524 by the address setting unit of the own node.
01 (306 or 321.331.341. in Figure 4)
351), and the comparison result is output to the control unit 310. The frame to be transmitted is sent from the control unit 310 to the transmission buffer 5.
11, and then sent from the transmitting circuit 510 to the communication medium via the interface section 502. The communication control of this system will be explained below. First, communication control of the host will be explained with reference to a flowchart showing communication control of the host in FIG. In this system, all data communication between the host and No. 1 is performed by polling or selecting from the host. In other words, the host side takes the initiative in communication. If the host has data to be sent from its own host in step 100, the process proceeds to step 102 and generates a transmission frame as shown in FIG. In this case, priority is given to the setting value of the address setting section 501 of the node section as the source address 203, and the setting value of the address setting section 501 of the communication node 100 is given priority.
The setting address of 1 is sent as the source address 203. In data communication between the host and No. 1, unlike packet communication between nodes, which will be described later, all data that needs to be sent and received is transmitted at once. Subsequently, in step 104, a selecting frame shown in FIG. 3(B) is sent to the node. Then, in steps 106 and 108, it is monitored whether there is any received data (response) before timeout. If there is no received data, the process proceeds to step 122, where "E" is sent to the node.
OT" and returns to step 100 to perform selection again. In step 106, if there is received data, it is checked whether the received data is "ACK", and if it is not "ACK", the node prepares to receive data. In order to indicate that the data frame has not been completed, the process returns to step lOO and waits for reception preparation to be completed.If "ACK" is received, the process proceeds to step 11'2, sends the transmission data frame to the node, and then returns to step 100. A timeout is monitored at steps 114 and 116. In case of a timeout, the process proceeds to step 122 described above;
If the data has been received, the process proceeds to step 118 and checks whether the received data is "NAK".
In the case of "K", the transmitted frame was not correctly received by the node, so the transmitted frame is invalidated and the controller returns to Stella 7'112 to redo the communication control, and retransmits the transmitted data frame.If the received data is "NAK" ”, the process advances to step 120 to check whether there is an “ACK”, and if it is “ACK□’, the transmitted frame has been correctly captured by the node, so the process returns to step 100 and ends the data reception process, and “
If it is not “A CK”, the process goes to step 122 and “E
Send OT"" and return to step lOO. If there is no data sent from the host in step 100, the process proceeds to step 130, and the node is sent to the node as shown in FIG. 3(A).
Send the polling frame shown in step 132.
In step 134, wait for a response from the node until timeout. If there is no response, the process returns from step 134 to step 100. If there is a response, the process proceeds to step 136.
If it is an "EOT" response, it indicates that there is no data to be sent from the node to the host, so the process returns to step 100.If "EOT" is not received, a data frame is sent from the node. The received data frame is received in step 13g.Then, Stella 7'140 checks whether there is a reception error in the received frame using the data frame check code (BCC check code) 207.Reception If there is an error, proceed to step 142 and write “” to the node.
NAK''' is sent, the received frame is invalidated in step 144, and the process returns to step 132 to wait for the retransmission of the data frame. If the frame is correctly received in step 140, the process proceeds to step 146 and the node is sent to the node. ACK” is sent,
Subsequently, in steps 148 and 150, whether or not "E OT" is received is monitored until timeout. If the ACK'' code is correctly sent to the node and the data communication ends normally, the node sends the ``EOT'' code, and the process returns from step 148 to step 100 to prepare for the next data communication. If the "E OT" code is not sent and a timeout occurs, data communication will not be performed normally for some reason, and steps 150 and 152 will be performed.
Then, the received data is invalidated and the process returns to step Zoo. In the above explanation, when sending data to another host connected to the same node, the destination address 202
By specifying the own node address as , data can be sent from a host to another host via the node. Next, the communication control on the node side of node-host communication is
This will be explained with reference to the flowchart shown in the figure. A node starts operating upon activation (polling/selection) from the host. First, in step 200, the carrier detection unit 523 determines whether a carrier has been sent from the host.
Monitor by output, and if carrier is detected, step 2
00, the process proceeds to step 202, and the subsequently sent data is received. Then, in step 204, it is checked whether or not the received data is a selecting frame. If it is a selecting frame, the process proceeds to step 206, and it is checked whether the node can receive data from the corresponding host. If the data cannot be received, in step 208, "NAK'' is returned and the process returns to step 200. Step 2 in case of data reception Irf
Proceed to step 10 and return A CK”, then step 212, 2
14, it monitors for data to be received until timeout. In case of timeout, the process returns to step 200. When the data is sent, step 212 starts with step 2.
16, the data frame is received into the reception buffer 521. When the data reception is completed, in step 218,
Received frame check code (BCC code) 207
Check whether a reception error has occurred in the received frame. If there is no reception error, proceed to step 220, and A
CK'', completes the data reception process, prepares for transmission to the destination specified by the destination address 202, and returns to step 200. If there is a data reception error, the process proceeds to step 222;
It responds with "NAK", invalidates the received frame, returns to step 212, and waits for another frame to be sent. If it is determined in step 204 that a selecting frame has not been received, the process proceeds to step 226 to check whether the received data is a polling frame. If it is not a polling frame, the process returns to step 200. If it is a polling frame, proceed to step 230;
It is checked whether there is data to be sent from the node to the host, and if there is no data to be sent, the process advances to step 246 and "'E
OT'", and then returns to step 200. If there is data to be sent, a frame addressed to the host is sent in step 232, and then a response to the sent frame is waited for in steps 234 and 236. If there is no response until timeout If there is a response, the process proceeds to step 246, and if there is a response, it is checked in step 238 whether or not the response is 'NAK'. In the case of ""NAK", the process returns from step 238 to step 232, and the frame addressed to the host is sent again. If the received data is not "NAK", the process advances to step 240, and it is determined whether the received data is an "ACK'" response or not. If the response is "ACK", the frame was sent correctly, so the transmitted frame is erased in step 242, the process proceeds to step 246, "EOT" is sent, and the process returns to step 200.
Return to If the response is not "ACK" in step 240, it is determined that a communication error has occurred and the process proceeds to step 246, where the transmitted frame is not erased. In the above explanation, data exchange between a node and a host is all done in one communication, but in the communication between a node and No. 1 described below, the data is divided into smaller than a specified amount and divided into multiple times. Therefore, when all of the divided and sent data has been sent and received, communication between the destination node contending hosts is performed. Communication control between each node will be described below with reference to flowcharts shown in FIGS. 8(A) to 8(C). All communication between each node 1 is performed using a bucket frame shown in the second r54. First, in step 300 of FIG. 8(A), the carrier detection unit 523 checks whether a carrier is detected from the eight communication media. If a carrier is detected, a packet is subsequently sent, so in step 302 it is checked whether or not the carrier from the communication medium 100a in FIG. 4 has been detected by the transmission circuit A304. In this case, the process proceeds to “reception A” shown in FIG. 8(B), which will be described later, and the carrier from the communication medium
If it is detected in step 505, the process proceeds to the 81st m(C) "receiving B" process. If no carrier is detected in either step 300, the process advances to step 308 to check whether there is data to be transmitted to another node, and if there is no data to be transmitted, the process returns to step 300 to detect reception of data or request transmission. Loop until occurrence. If there is transmission data in step 308, step 3
Proceed to step 10 to check whether the destination node address is greater than the own node address. In this system, each node address is shown in Figure 4.

[(Connection node address to transceiver A302 side) < (own node address) <(')
Lancer B 303 (connection node address to Ill)] This is to determine from which transmission medium the transmission packet should be sent. If the destination address 202 is smaller than the own node in step 310, it is sufficient to send it to the communication medium 100a, and in step 312 the packet is sent to the transmission buffer 511 of the transmission circuit A304, and in step 314 from the transceiver A302. Send the transmission packet and return to step 300. When the destination address 202 is larger than the own node address in step 310, it is sufficient to transmit to the communication medium 100b side, and in steps 316 and 318, similarly to steps 312 and 314, transmission circuit B5
05, transceiver B 503 transmits a repacket and returns to step 300. Next, reception processing will be explained. When a carrier is detected from the transmission medium 100a, the process proceeds to the "reception A" process shown in FIG. 8(B) as described above. First, in step 320, a received packet from the communication medium 100a is sent to the transmission circuit A304 via the transceiver A302.
The received data is received in the receive buffer 521 of. and step 32
2, it is determined by the check code 207 whether a reception error has occurred or not. If a reception error has occurred, the process advances to step 324, and the transmission circuit A304 outputs “N A
K” prepare to send packet, step 3
In step 26, the data stored in the reception buffer 521 is invalidated and the process returns to step 300. If no reception error has occurred in step 322, the process proceeds to step 330, where the address data value stored in the address register 522 from the receiving circuit 520 in FIG. Then, it is checked whether the received packet is an "ACK" packet addressed to its own node. If it is an "ACK" packet addressed to its own node, the transmission of the corresponding packet is completed in step 332, so the corresponding packet is sent. Clear and step 3
At step 34, the reception eight buffer is cleared and the process returns to step 300. If it is determined in step 330 that the packet is not addressed to the own node, the process proceeds to step 336, and step 320
In the same way as tfB524, the “NAK” addressed to the own node is sent.
Check whether it is a ``'' packet. If it is a ``NAK'' packet addressed to the own node, proceed to step 338, perform SSS transmission to retransmit the corresponding packet, and proceed to step 334. ``A'' in explanation 1 above. CK ``Packet and'' N
The ``AK'' packet is specified as an ``ACK'' packet or a N AK '' packet in the transmission command 204 shown in the second [ffl. This transmission command consists of 2 bytes, the first byte is for node-to-node communication and has the structure shown in Table 2 below. Table 2 The second byte is for communication between the packet source node and the packet destination node 1, and its structure is shown in Table 3. Table 3 Now, if it is determined in step 336 that the packet is not addressed to the own node, the process proceeds to step 340, and it is checked whether it is an "ACK'" packet addressed to another node. “ACK/NA” indicates whether the received packet is normal or abnormal.
In this case, if the packet sequence numbers are not consecutive, a "N A K" packet is sent to request retransmission, and all communications are completed normally.
In this case, an "ACK" packet is sent. In this case, since no response is made to the received packet, the process proceeds to step 348, which will be described later. If it is determined in step 340 that the packet is not an "ACK/NAK" packet addressed to another node, the process proceeds to step 342, and the comparing unit 524
It is checked from the output whether the received packet is a data packet addressed to the own node, and if it is a data packet addressed to the own node, the process proceeds to step 344, where it is checked whether it is the last of the communication data. If the communication data is the last, all data communication from the source node has ended normally, so the process advances to step 346, where the transmission circuit A prepares to send the source node "ACK" packet and returns to step 300. The prepared transmission packet is transmitted. If it is not the end of the communication data, the process advances to step 347, and the transmission circuit A 304 prepares to transmit an 'A CK' packet in response to the received packet, and the process advances to step 348. If it is determined in step 340 that the packet is an "ACK/NAK" packet addressed to another node, the process similarly proceeds to step 348, where it is checked based on the output of the comparator 524 whether the destination address 202 is larger than the own node address. If it is larger than the own node address, the process proceeds to step 350, prepares to transmit the received packet from the transmission circuit B505, and returns to step 300. If the destination address 202 is smaller than the own node address, the received packet is invalidated and not transmitted to the transmission circuit B505. Then, the process returns to step 300 in the same manner. This is because there is no node on the communication medium toob side that has a node address smaller than its own node address. Further, if the carrier is detected in the transmission circuit B505 in step 302 of FIG. 8(A), the eighth
The process proceeds to "receiving B" shown in FIG. 3(C). In the "receiving B" process, the same processing as "receiving A 11" is performed in the transmission circuit B505, but the "receiving A
"Processing A In the processing after step 348, step 3
Similarly to No. 48, the comparison unit 524 checks whether the destination address 202 is larger than the own node address, but in this case, if the destination address 202 is smaller than the 0 node address, the received packet is prepared to be transmitted from the transmission circuit A 304, If the destination address 202 is greater than the own node address, the received packet is invalidated. This is because there is no node on the communication medium 100a side that has a node address larger than its own node address. In the following E explanation, d! The connection and operation of the single value medium 100 was performed using a normally closed relay, and the relay contact was opened/closed by turning on/off the power source of the notebook, but when a node actually participates in the network. For example, when there is no data on the communication medium, by connecting the relay contact and controlling the transmission, there will be no negative impact on the network even if the data cannot be transferred due to malfunction of the node. Connection, separation, and control of communication media can be performed. [Effects] As described below, according to the present invention, it is possible to provide a transmission device in which the control of the entire network does not stop even if the transmission devices constituting the network stop or the power is cut off.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a network system configuration according to the present invention, FIG. 2 (A) is a diagram showing a packet communication frame in the network system according to the present invention, and FIG. ), FIG. 3(A) shows the polling frame in communication between the transmission device and the host of the network system according to the present invention, and FIG. 3(B) shows the details of the address part of the packet frame shown in FIG. FIG. 4 is a block diagram of a transmission device according to an embodiment of the network system according to the present invention, and FIG. 5 is an embodiment shown in FIG. 4. A diagram showing details of the transmission circuit section of the transmission device, FIG. 6 is a communication control flowchart of the host connected to the transmission device of this embodiment, FIG. 7 is a flowchart showing the communication system @ of the transmission device of this embodiment with the connected host, FIGS. 8(A) to 8(C) are flowcharts showing communication control procedures between the transmission devices of this embodiment. In the figure, 100.100a, 100b, - communication medium,
lO1~105.300...Node, 111 N11
4,401-404...Host, 301...Line connection control unit, 302,303...Transceiver, 304
,305,322,332,342,352,500・
...Transmission circuit, 30B, 321, 331, 341, 35
1,501... Address setting section, 310... Control section, 323, 333, 343, 353... Transmission interface, 502... Interface section, 510...
・Transmission circuit, 511... Transmission eight-fa, 520...
Receiving circuit, 521... Reception eight buffer, 522... Address register, 523... Carrier detection section, 524
...This is the comparison section. Figure 1 Figure 2 (A) Figure 3 (A) Figure 3 (B)

Claims (2)

[Claims] (1) The transmission device of a network system in which a plurality of transmission devices are connected in series via communication media to perform data transmission, and the communication medium connection means separates and connects the communication media connected to other transmission devices. characterized in that the communication medium connecting means controls to connect the communication media to each other when the transmission device is stopped, and to separate the communication media from each other when the transmission device is in operation. transmission equipment. (2) The transmission device according to claim 1, wherein the communication medium connection means is composed of an electromagnetic relay, is always in a closed state, and becomes an indirect state when the power of the transmission device is turned on.