JPS60117846A - Data transmission system - Google Patents

Abstract

PURPOSE:To couple various devices through a single bus by applying bus competition with a simple packet ahead a data and transmitting the data between external devices in a free data from after a link is established. CONSTITUTION:Suppose that a data is transmitted from a serial transmitter 13 to a serial transmitter 14, a packet 22 is transmitted from a controller 15, an ACK 23 is transmitted from a controller 16 and a data 24 is transmitted from the transmitter 13. Then the data 24 is transmitted directly to the transmitter 14 via the controller 16 and the modification or the like of the data form is not applied. When the 3rd party observes the data flow, since the data 22 is apart from the packet 21 by a required minimum packet interval Tp or over, it is discriminated as a packet and it is known that the packet is not addressed to itself throgh the decoding. Since the ACK(NAK) 23 and the data 24 are not apart from the preceding data string respectively from the Tp or over, they are discriminated that they are not packets and skipped and the transmission of the next packet is inhibited for the time.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a data transmission system for transmitting and receiving data at various transmission speeds and in non-uniform data formats via a network.

<Prior art> In order to protect the data on the bus, the bus-based networks that have been proposed so far can only handle packet data whose data format, timing, and transmission speed are precisely specified. When transmitting and receiving data over a network, it is necessary to pass through a gateway that has functions such as packetization. As an example, consider a display connected to a computer. For the sake of simplicity, it is assumed that the connection is made through an R8232C interface.

To connect these two via a network, data sent from the Zuzu computer is output to the gateway via the R8232C, the gateway packetizes the data, performs bus arbitration such as timing, changes the data format, and transmits the data on the bus. Send to.

This packet is taken into the gateway at the receiving end, parts of the packet other than data are removed, the data format is changed, and the data is sent to the display via the R8232C line on the secondary side and displayed. As can be seen in this example, even though the data format is unified between computer displays, it is impossible to change the data format twice due to the intervening network. It is also necessary to prepare various gateways depending on the type of data format of the secondary side transmission path. For example, odd-even parity, synchronous/asynchronous, bit length, etc. must all be adjusted to the external device.

<Objective of the Invention> The present invention performs only bus contention using simple packets before transmitting data, and after a link is established with the other party, data is transmitted between external devices via the bus in a free data format. This data transmission system allows various devices to be connected via a single bus.

<Embodiment> An embodiment of the method of the present invention will be described below with reference to the drawings. FIG. 1 is an example of a system configuration to which the present invention is applied. In the figure, 10 is a bus-type network, 11◆12
is a station (i-device) connected to the network,
Reference numerals 13 and 14 indicate external devices having a different type from the station, for example, having a serial transmission function, and 15 and 16 indicate simple-structured transmission control devices connected between the external devices 13 and 14 and the network.

FIG. 2 is a timing chart showing the flow of data on the network. Note that the packet referred to here is a simple packet that includes a destination address, a self address, a control word, a check code, and the like.

In the figure, 21 and 22 are packets, and the interval T1 between the packets 21 and 22 is kept equal to or greater than the required minimum packet interval Tp. 2
3 is an ACK (NAK) for the packet 22, and the interval T2 is selected to be less than or equal to Tp. Because T2 > T
If p, there is a possibility that another packet will interrupt during this time, and in that case, 23 is the ACK (
This is because you will not be able to understand NAK). 24 is data sent from the serial transmission device 13 or 14 in a unique format. ACK (NAK) 23 and data 24
It is also better to set the interval T3 smaller than Tp.

This is because if T3>Tpk, the data 24 may be misunderstood as the next packet.

Now, assuming that data is sent from the serial transmission device 13 to the serial transmission device 14, the packet 22 is sent from the control device 15 to the serial transmission device 14.
CK23 is sent from the control device 16, and data 24 is sent from the serial transmission device 13. and data 2
4 is sent directly to the serial transmission device 14 via the control device 16, and the data format is not changed at this time. When a third party, for example station 11, looks at the flow of this data, data 22 is determined to be a packet because it is more than Tp away from the previous packet 21, and by decoding it, it can be seen that it is not addressed to itself. Then ACK (NAK) 23
- Since each data 24 is not separated by more than Tp from the previous data string, it is determined that it is not a packet and is skipped, and at the same time, the transmission of the next packet is also prohibited during this time, and the data is likely to be destroyed.

Although the figure describes the case with ACK, the same applies even if ACK is not required. In this case, T2 and ACK (NAK) 23
is deleted from the diagram.

I'll explain it in a little more detail now.

FIG. 3 is a block diagram showing details of the transmission control devices 15 and 16 shown in FIG. 1. 30 is a transmitter, 31 is a receiver, 32
is a data detection section, 33 is a transmission control section, and 34 and 36 are 7 real data lines and transmission request signal lines from the serial transmission device 13 or 14, respectively, 35, 37, and 38.
are the reception cheater line, transmission permission signal line, and reception request line of the Norial transmission device 13 or 1, respectively.

FIG. 4 shows the timing on each line, and FIG. 5 shows the operation flow in the transmission control devices 15 and 16.

In Figure 5, for the sake of simplicity, we have shown for transmitting (a) and receiving (b)
), but it is of course possible to have both functions in one device.

When transmitting 7 real data from the external serial transmission device 13 (or 14), first, a transmission request signal is output to the control unit 33 of the transmission control device 15 (or 16) through the line 36. Upon receiving this signal, the control section 33 controls the O of the transmitting section 30.
The packet 41 is sent to the network 10 via the R gate by line contention. As described above, from the previous bucket) 21, 22, ACK 23, and data 24 (see FIG. 2), transmission is possible only when there is no data on the network 10 for a period of at least Tp or more.

The line is established by sending packet 41 with permission to send and receiving ACK 42 from the other party who received this packet.
~Know things. Therefore, after T4 has elapsed, the control device 15 (or 16) tells the serial transmission device 13 (or 14),
After outputting a transmission permission signal through line 37, the serial transmission device 13 (or 14) immediately outputs serial data through line 34. Part 1: This serial data can be changed by the control device 15 (or 16).
The data is sent to the network 10.

The transmission permission signal on the line 37 is transmitted to the serial data 4 by the operation of the receiving section 31, the data detecting section 32, and the control section 33.
3 continues until there is no data for a predetermined period of time or the transmission request signal on line 36 becomes inactive.

Similarly to the transmitting side, the control device 16 (or 15) on the receiving side can receive the packet only when there is no data on the network 10 for a period of at least Tp or more from the previous packet, ACK, and data.
If it is addressed to you, send back ACK43 within a predetermined time. After returning ACK43, the predetermined time T5 (<T4
) After that, a reception request signal is output to the 7-real transmission device 14 (or 13) through the line 38. The serial transmission device 14 (or 13) I-1 can receive only necessary data by taking in data through the line 35 only while the reception request signal is active.

In the above, D-43 after receiving ACK42 on the sending side
Period until transmission and A after receiving packet 41 on the receiving side
The period until CK42 transmission is selected to be less than or equal to the required minimum bucket interval Tp, and a third party can determine that the packet is not a packet and skip it.

<Effects of the Invention> As described above, the data transmission system of the present invention sends a packet on the network by contesting a line in response to a request from the outside, and outputs a transmission permission signal to an external device only when the contention is successful. On the other hand, addressed to yourself? When receiving Kent,
It outputs a reception request signal to an external device and allows the data part to pass through as is, allowing data to be sent and received between external devices without being aware of the network, and also sets the minimum allowed packet interval. By doing so, it is possible to determine whether a packet is a packet or other data that is not addressed to it by a simple time comparison, and a third party can skip the subsequent data that is not addressed to him and at the same time prohibit the sending of the next packet, thereby preventing the third party from transmitting the next packet on the network. It is possible to prevent data 1 from being destroyed.

[Brief explanation of drawings]

Figure 1 is a system configuration diagram to which the present invention is applied, Figure 2 is a diagram showing the timing of data on the network, and Figure 3 is a diagram showing the timing of data on the network.
1 is a block diagram of the main part of the apparatus shown in FIG. 1, FIG. 4 is a timing diagram on each page of FIG. 3, and FIG. 5 is a flow chart explaining the operation of FIG. 3. 10...Network, 11/12 Station, 1
3.14.Serial transmission device, 15.16..Transmission control device, 21.22..Bakunodo, 23..ACK (N
AK), 24...Data, 30 Transmission unit, 31...Reception unit, 32 Data detection unit, 33-Control unit, 41...Packet, 42-ACK, 43 Data 0 Agent Patent attorney Aihiko Fukushi ( 2 others) Figure 1 Figure 3 (G) (b) 55! !

Claims (1)

[Claims] 1. In a system where multiple devices with different processing capabilities coexist in the same network, only when a network line is contested, packets with the transmission speed and format defined by the system are sent, and after the network is secured, 1. A data transmission system, characterized in that data transmission is performed at a transmission rate and format specific to a device, and a minimum permissible kerat interval is set for said packet.