JPH0145785B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission system between information processing devices or between a main device and a slave device of information processing devices. In particular, the present invention relates to a data transmission method in which data is sent and received via a bus line using a handshake method.

In the handshake method, a means for transmitting control signals is installed along with the bus line that transmits data, and a command signal is transmitted from a station that is a talker that transmits data to a station that is a listener that receives data. Depending on the signal, the station acting as a listener sends a response signal back to the station acting as a talker, depending on its state.
This is a method of sending and receiving data on a bus line. The control signal transmission path can be provided in a space-division manner or a time-division manner with respect to the bus line for transmitting data.

The handshake method is widely used because it allows devices with different response speeds to be connected to a common transmission path and is an excellent method that ensures extremely reliable data transmission and reception. This handshake method is also implemented in a method in which a number of stations are branch-connected to one bus line, one of which serves as a talker and a plurality of other stations serve as listeners. In this case, the control signal transmission path is connected, for example, by wired-OR at each station.

However, in the conventional method, each station is connected in a branched manner.
As the number of stations to be connected increases and the distance to those stations increases, the number of connection points and repeaters increases, the signal load increases, the delay in the transmission path increases, and communication efficiency decreases. There are disadvantages such as.

In the present invention, each station is connected in a loop by a bus line, and on this loop-connected bus line, a signal is transmitted from a station serving as a talker via each station serving as a listener.
The signal frame returning to the station serving as the talker is configured to be relayed and transmitted. This signal includes the time domain of a command signal that is commonly transmitted from a talker station to a listener station, and the time domain of a response signal that is commonly used and transmitted from a listener station to a talker station. Configure to contain a region. A station serving as a listener writes and transmits the logical product or logical sum of the received response signal and the logical value of its own station's response signal in the time domain of the response signal, and the station serving as a talker writes and transmits the logical value of the received response signal and the logical value of its own station's response signal. It is characterized in that it is configured to control the next transmission step based on the received response signal.

This will be explained in more detail using the drawings.

FIG. 1 is a time chart showing a conventional handshake method data transmission procedure. DATA
indicates the timing of data sent on the bus line from the station serving as a talker. Signal line
A command signal is sent to DAV (DATA VALID) from a station that is a talker to a station that is a listener. Signal line NRFD (NOT RADY
FOR DATA) and NDAC (DATA NOT
ACT), a response signal is transmitted from a station that is a listener to a station that is a talker.
When the talker station sets the signal line DAV to logic "1", the listener station responds by setting the signal line NRFD to logic "1".
The talker station that receives this changes the signal line DAV to logic "1" if the data being sent to that bus line is to be valid. The station serving as a listener takes in the data on the bus line and sends a logic ``1'' to the signal line NDAC.
At the talker station that receives this,
Send logic ``1'' to the signal line DAV and move on to the next cycle.

When a plurality of stations serving as listeners are connected to this transmission path, each signal line is connected, for example, in a wired-OR manner.

In this manner, in the handshake method, data is transmitted while transmitting and receiving control signals in one cycle. As the number of stations connected to a transmission path increases, it is inevitable that the load and delay will increase.

FIG. 2 is a station connection diagram according to an embodiment of the present invention. The four stations S ₁ to _{S 2} are connected by a bus line L in a loop. A device E is connected to each of the stations S ₁ to _{S 4} either singly or by another branch-like bus line L'. Here, the stations S ₁ to _{S 4} are configured to mutually transmit and receive data using a handshake method.

That is, when S ₁ becomes a talker and another station becomes a listener, a frame signal having a frame structure as illustrated in FIG. 3 is transmitted from the station S ₁ to the bus line L. This frame signal includes a frame identification code F and a data area.
In addition to DATA, there is also an NTC (NEW TRANSMISSION) indicating data transmission of a new cycle.
CYCLE) code and DAV (DATA VALID) code are inserted between the frame identification code and the data area, and after the data area, NRFD (NOT
READY FOR DATA) code and NDAC
(NOT DATA ACT) A code area is placed.

FIG. 4 is a block diagram of essential parts of a station according to an embodiment of the present invention. The signal on the bus line L is input to the receiving circuit RX, and the digital signal is amplified and reproduced. The output of the receiving circuit RX is the switching circuit SW
It is connected to the first contact point 1 of. The output of the receiving circuit RX is branched and connected to one input of the OR circuit O. The other input of this OR circuit O is a control signal input.
Sin is connected. The output of the OR circuit O is connected to the second contact 2 of the switching circuit SW. Receiving circuit RX
The output of is further branched and connected to the data output Dout. A data input Din is connected to the third contact 3 of the switching circuit SW. The output of the receiving circuit RX is led to a control circuit TC, and a control signal output Sout is sent to the output of this control circuit TC. Furthermore, the switching circuit SW is controlled by the output of the control circuit TC.
The output of the switching circuit SW is transmitted from the transmitting circuit TX to the bus line L of the next section.

In the device configured as shown in FIG. 4, the switching circuit SW is initially connected to the first contact 1. Third
When the frame signal explained in the figure is received, the control signals NTC and DAV are separated and output to the output Sout. If the data of this frame signal is received at that station, it is retrieved from the data output Dout. When transmitting data to this data area in this station, the switching circuit SW is connected to the third contact 3 at the timing of the data area.
and insert data from the data input Din. At the timing of the control signal following the data area, the switching circuit SW is switched to the second contact 2,
The output of the OR circuit O is transmitted to the bus line L. The output of this OR circuit O is the logical sum of the logical value of the control signal in the received frame signal and the logical value of the control signal of the own station.

In this way, each station shown in FIG.
When the frame signal is relayed and transmitted at S ₂ to _{S 4} and returned to station S ₁ , one cycle of data transmission using the handshake method has been executed.

Each station distributes necessary data to the devices E connected to each station.

The present invention is suitable for implementation in an optical communication system using an optical fiber as a transmission path.

Although the above example describes an example in which there are four types of control signals for handshake, the present invention is not limited to these types of control signals, and the present invention can be implemented with various types of control signals.

As explained above, according to the present invention, even if the number of stations is n, data transmission and transmission control by handshake can be performed by sending and receiving a frame signal once, so that the number of stations can be n. Even if the number of channels increases, the delay in the transmission path can be reduced, and the transmission efficiency can be improved.

In addition, data can be transmitted reliably without losing the advantages of the handshake method, the number of connection points and repeaters can be reduced, and branch connections can be made even if stations are located in the same geographical location. Compared to the conventional case, the distance of the bus line is shortened, and the entire transmission system can be constructed economically.

[Brief explanation of drawings]

FIG. 1 is a time chart explaining the handshake type communication control operation. FIG. 2 is a diagram illustrating a transmission line configuration according to an embodiment of the present invention. FIG. 3 is a configuration diagram of the frame signal. FIG. 4 is a diagram showing the main parts of a station according to an embodiment of the present invention. S ₁ ~S ₂ ... Station, E ... Device, L ...
Looped bus line.

Claims (1)

[Claims] 1. One or more talker stations and two or more listener stations are connected by a bus line, and data is transmitted from the talker station to the listener station by a handshake method. In this method, each of the stations mentioned above is connected in a loop by a bus line, and on this loop-connected bus line, transmission is transmitted from the station serving as the talker via each station serving as the listener, and then to the station serving as the talker. The signal frame includes a command signal that is commonly addressed from the talker station to the listener station, and a command signal that is commonly used by the listener station. The listener station performs a logical product of the logical value of the received response signal and the logical value of its own station. Alternatively, a loop characterized in that the logical sum value is written in the time domain of the response signal and transmitted, and the station serving as the talker is configured to control the next transmission step based on the received response signal. Handshake transmission method using bus.