JPH0525215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a data transmission system in a data way system, and particularly to a busy monitoring system on the data receiving side.

2. Description of _the Related Art A data way system is _a ring- _shaped data way system, for example, as shown in _FIG . One or more terminal devices 3 ₁ to 3 _o including computers are coupled to the terminal devices, and data reception between the terminal devices is performed via data stations 1 ₁ to _{1 4} and transmission lines 2 ₁ to 2 ₄ .

In data transmission of data way system,
Since the sending side can control the timing of data transmission by itself, it is easy to manage the sending buffer. On the other hand, since the receiving side receives data from the transmitting side at arbitrary timing, managing the receiving buffer becomes a problem.

Conventional reception buffer management includes the following three methods.

(1) A method of having multiple receive buffers and switching between them to acquire data.

(2) A method in which the sending side checks the availability of the receiving buffer and sends data.

(3) A method in which the sender sends data at sufficient time intervals to allow the receiver to process the received data.

Problems to be Solved by the Invention In the conventional method (1), if data exceeding the reception buffer capacity is continuously sent, data reception becomes impossible. In addition, the number of reception buffers is determined from the amount of data concentrated on one station depending on the system to which it is applied, but it is difficult to determine the appropriate number of buffers from consideration of the entire system configuration, so it is natural to increase the margin. This increases the number of buffers required, leading to increased costs.

In the conventional method (2), only one reception buffer is required, but the transmission control procedure (protocol) becomes complicated, making system start-up difficult. Furthermore, since the transmission procedure involves checking the status of the receiving buffer (empty, busy) before data transmission, the overhead of data transmission becomes large, leading to a decrease in transmission efficiency.

With the conventional method (3), when data is concentrated on one data station from multiple data stations, it is difficult to control the timing of each transmission data, and the transmission interval has to be made larger than necessary. . Further, securing an interval on the transmitting side imposes a large restriction (burden) on the applied system when configuring the transfer system.

Means and Effects for Solving the Problems The present invention provides a communication control section provided in a data station with a reception buffer that indicates whether the reception buffer is in an empty state or a busy state when transferring data to the reception buffer of a terminal device interface section. Provide a status register, prohibit rewriting of the register during transfer of received data, and detect whether the receive buffer is empty or busy from the state of the register at the end cycle of the received data. It is characterized by

Embodiment FIG. 1A is a data station block diagram showing an embodiment of the present invention, and the station ₁₁ in FIG. 3 is representatively shown. In FIG. 1A, two terminal devices 3 ₁ and 3 ₂ are connected to one data station 1 ₁ , and data is transmitted to and from other stations via a ring-shaped transmission path 2 ₁ . The frame format of the transmission data exchanged between the data station ₁₁ and the transmission line ₂₁ includes, in addition to the information field, the destination data station address, destination terminal address, control field,
Exchange information such as destination data station address and source terminal address, as well as data for data check and frame synchronization, are attached.

The data station ₁₁ has a transceiver section 11 that mutually converts signals on the transmission line ₂₁ and electrical signals within the station, and a transceiver section 11 that mutually exchanges serial input/output signals of the transceiver section 11 with parallel signals on the internal bus 12. a communication control section 13 that transmits received data at high speed to an interface section of a selected terminal device based on terminal address data; and a terminal device 3;
a transmission control unit 14 that performs protocol processing, etc. for exchanging information with ₁ and 3 ₂ and executing transmission procedures;
The communication control unit 13 includes terminal interface units 15 ₁ and 15 ₂ that have buffers for data transmission and reception and have a function of absorbing the difference between the data transfer rate specified by the transmission rate and the data transfer rate of the terminal device. , transmission control section 14, and interface sections 15 ₁ and 15 ₂ are connected by an internal bus 12 containing terminal data, and information is exchanged between them.

Here, the interface units 15 ₁ and 15 ₂ each include one reception buffer 16 ₁ and 16 ₂ .
The transmission control unit 14 monitors the status of the reception buffers 16 ₁ and 16 ₂ (empty or busy), and if the reception buffers 16 1 and 16 2 are empty, the reception data from the communication control unit 13 is stored. Part 15
A notification of reception completion is sent to the end device _{3 1} or 3 ₂ via the terminal 3 1 or 15 ₂ . The reception buffers 16 ₁ and 16 ₂ are busy storing data and cannot receive the next data. This receiving buffer becomes empty when the terminal device transfers the data in the receiving buffer to the internal memory of the terminal device, and the interface sections 15 ₁ , 15 ₂
This is when the empty state of the reception buffer is notified to the transmission control unit 14 via the . Receive buffer 16 ₁ ,
16 ₂ faces toward the terminal devices 3 ₁ and 3 ₂ when in a busy state, and allows access from the terminal devices, but writing from the communication control unit 13 side is prohibited. Conversely, when it is in an empty state, access from the terminal devices 3 ₁ and 3 ₂ facing the bus 12 is prohibited, but access from the communication control unit 13 and transmission control unit 14 is allowed.

The terminal devices 3 ₁ , 3 ₂ have reception buffers 16 ₁ , 16 ₂
It recognizes the status (empty, busy) of each receive buffer 16 and stores the status in the receive buffer status register (RBSR) of the communication control unit 13.
Each time the status of ₁ , 16 ₂ changes, the corresponding register (RBSR)
Update the contents of. The communication control unit 13 requests the transmission control unit 14 for the right to use the bus 12 in order to receive data addressed to its own station, and upon receiving permission to use the internal bus from the transmission control unit 14, is occupied and the received data is transferred at high speed to the reception buffer of the interface section by DMA transfer.

Data storage in the receiving buffers 16 ₁ and 16 ₂ is as follows:
Data reception from the partner station (sender) and terminal device 3
Since the notification of availability from ₁ and 3 ₂ is carried out asynchronously, when the state changes from busy to vacant during data reception, the middle of the received data is stored in the reception buffer. Therefore, when the communication control section 13 transfers the received data addressed to its own station to a desired reception buffer, the transmission control section 14 detects whether the buffer is in a busy state or in an empty state.

This detection is explained by the time chart shown in FIG. When there is received data addressed to the own station, the communication control section 13 issues a request signal HLDR for the right to use the internal bus to the transmission control section 14. In response to this request, the transmission control unit 14 issues a bus right permission signal HLDA. At this time, since the internal bus 12 is occupied by the communication control section 13, the transmission control section 14 cannot use the internal bus. In addition, during the period THA when the signal HLDA is output, the reception data transfer to the reception buffer is performed by the reception data DAM transfer request signal RDRQ and the memory write MWR. Reception buffer status register of control unit 13
The contents of RBSR will not be rewritten.

In this state, at the end cycle (time t ₁ ) of DAM transfer of received data, the communication control unit 13 releases the bus right request signal HLDR. At this time,
Prior to releasing the bus right permission signal HLDA, the transmission control unit 14 samples the corresponding bit of the reception buffer status register RBSR of the reception buffer, and determines the status of the reception buffer that has completed reception. This is because the contents of the register RBSR in the communication control unit 13 do not change even if the state of the receive buffer undergoing DAM transfer during reception changes from a busy state to an empty state due to an empty signal from the terminal device. This is because it is possible to know whether the end cycle is in a busy state or not.

At the same time as the signal HLDA is released, the transmission control section 14 generates a reception completion interrupt from the communication control section 13 and a terminal interface interrupt from the interface sections 15 ₁ and 15 ₂ (generated by an empty command from the terminal device). By giving a higher priority to the reception completion interrupt, the transmission control unit 14 can know whether the destination of the received data is busy or free from the sampled reception buffer status. .

A state storage circuit of the reception buffer in the communication control section 13 is shown in FIG. 1B. In the figure, 21 is the receive buffer status register (RBSR), and its contents and terminal address register (TAR) 2
The multiplexer 23 extracts the state of the reception buffer from the contents of 2, and this state signal is ANDed with the reception enable signal Enable addressed to the own station in the AND circuit 24, and the flip-flop 25 as the reception buffer state memory is set. The flip-flop 25 is reset by the received data end cycle signal End.

Note that the processing content of the transmission control unit 14 changes depending on the state of the reception buffer (empty or busy) at the time of completion of reception, but this processing will be omitted.

Effects of the Invention According to the present invention, one reception buffer is prepared in association with a terminal device coupled to a data station, a register is provided to indicate whether the reception buffer is empty or busy, and reception data addressed to the own station is Prohibits rewriting of the register during transfer to the reception buffer,
By sampling the corresponding bit of the register at the end cycle of the received data, it is possible to detect whether the receiving buffer to which the received data has been transferred is empty or busy. There is no need to use a protocol to check buffer availability, there is no need to take a transmission interval, and management is facilitated while reducing buffer capacity and increasing transmission efficiency.

[Brief explanation of drawings]

FIG. 1A is a data station configuration diagram showing an embodiment of the present invention, FIG. 1B is a receiving buffer state detection circuit diagram of the communication control section 13 in FIG. 1A, and FIG. 2 is a receiving state detection circuit diagram according to the present invention. The time chart, FIG. 3, is a schematic diagram of the loop data way system. 1 ₁ , 1 ₂ ... data station, 2 ₁ , 2 ₂ ...
...Transmission line, 3 ₁ , 3 ₂ , 3 _o ...Terminal device, 11...
...Transceiver section, 12...Internal bus, 13...
Communication control unit, 14...Transmission control unit, 15 ₁ , 15 ₂
...Interface section, 16 ₁ , 16 ₂ ... Reception buffer, 21 ... Reception buffer status register, 22 ... Terminal address register, 2
3...Multiplexer.

Claims (1)

[Claims] 1 Connect each data station with a transmission line,
In a data way system that transmits data between terminal devices connected to each data station, the data station has a communication control unit that converts received data into parallel data and transfers it to a reception buffer provided in the terminal device interface. The communication control unit is provided with a reception buffer status register indicating whether the reception buffer is in an empty state or a busy state,
Rewriting of the register is prohibited during transfer of received data, and whether the receive buffer is empty or busy is detected from the state of the register at the end cycle of the received data. Busy monitoring method for data transmission.