JP3230339B2 - Communication control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control device which is disposed between a terminal device and a transmission line and executes a communication process according to the priority for a plurality of types of communication requests having different priorities. About.

[0002]

2. Description of the Related Art Generally, in a communication system, a plurality of types of communication requests having different communication priorities are often mixed. For example, in a system that requires real-time communication,
Communication control in which a request for real-time communication is set to the highest priority is required. Conventionally, as a communication control device that processes such communication requests having different priorities, a communication control device that determines the nature of the communication request by software processing and assigns a priority to the communication request, or a communication control device that has different priorities in advance. A first-in first-out memory (FIFO) is provided to store data in a FIFO corresponding to the priority of a communication request, and to execute communication processing in order from the data stored in the FIFO with a higher priority. JP-A-4-34
No. 4550) is known.

[0003]

However, among the above-mentioned conventional communication control devices which are controlled by software, the higher the communication speed, the higher the performance of C.
A PU is required, which increases the cost of the system and increases the overhead of software processing. On the other hand, in the case of a method using a plurality of FIFOs, the FIFO is usually constituted by a static RAM or the like having a large layout area.
There is a problem that the space occupation ratio of the FO increases, and as a result, the scale of hardware increases. Further, in this method, FIFO is provided for each priority, so that when communication requests of a specific priority are concentrated, another FIFO is provided.
Despite having enough free space in O, a specific FIFO
Information is stored centrally. For this reason, there is a problem that the memory cannot be used efficiently.

[0004] The present invention has been made in view of such problems, and reduces software overhead.
An object of the present invention is to provide a communication control device capable of improving the use efficiency of a memory and reducing the scale of hardware.

[0005]

[0006]

Communication control device according to this invention SUMMARY OF THE INVENTION, in the communication control apparatus for performing communication processing corresponding to the priority to priority different kinds of communication requests, A single-system first-in first-out storage unit that stores at least a part of information to be communicated in accordance with the plurality of types of communication requests having different priorities; and a communication control unit that sequentially reads information stored in the first-in first-out storage unit and performs communication processing. Means, when a communication request having a higher priority than the preceding communication request is generated, determining whether communication is currently in progress or waiting based on the communication status of the communication control means. If the communication process is interrupted, the high-priority communication request is processed. After the request is processed first, a priority control unit for processing the preceding communication request is provided. In the above communications controller, when the communication request higher priority than the communication request preceding occurs, the pointer of the high priority in the priority control means is set, on the set pointer The first-in first-out storage means may be configured to store the data in the first-in first-out storage means.

[0007]

According to the first communication control apparatus of the present invention, when a communication request having a higher priority than a preceding communication request is generated, the communication request having the higher priority is stored in the first-in first-out storage means at the break of communication processing. , And the higher priority communication request is processed with priority. Since the first-in first-out storage unit is a single system, both high-priority information and low-priority information are stored in the same first-in first-out storage unit. For this reason, it is not necessary to secure an extra storage area according to the priority, so that the use efficiency of the memory is improved and the storage capacity is small. Further, since a communication request with a high priority is processed at a break of a preceding communication process, incomplete data is not sent to the transmission line, and the transmission line is not damaged.

Further, according to the second communication control device of the present invention, when communication of a preceding communication request is currently being performed, the communication control device waits for a break in the communication processing, and the preceding communication request is on standby. In some cases, since information is discarded and high-priority information is communicated first, maximum priority processing can be performed as long as the transmission path is not damaged.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of one station (node) in the communication system according to the embodiment of the present invention. In FIG. 1, the station includes a communication control device 1 and a terminal device 2. The communication control device 1
It is interposed between the terminal device 2 and a communication line (not shown), and executes a communication control process according to the priority in response to a communication request given from the terminal device 2. Various methods are known as priority control methods.
As shown in FIG. 2, a plurality of stations 3a, 3b, 3c are connected to a ring-shaped network 4 and perform a priority control of a token ring system in which an access right is secured by the priority of a token circulating on the network. And

The terminal device 2 of each station is provided with a CPU 11 and a system memory 12 for storing information such as data and commands relating to communication requests. The communication control device 1 of each station has a first-in first-out memory (FIFO) 1
3, a communication control unit 14, a queue control unit 15 and a data control unit 16 as priority control means.

The FIFO 13 has a function of temporarily storing communication information created on the system memory 12 under the control of the data control unit 16 and sending the communication information to the communication control unit 14. One unit (packet) of communication information may reach as much as 1 kbyte, but the FIFO 13 has a small capacity of, for example, about 16 bytes. This is because data waiting in the FIFO 13 may be substantially discarded as described later, and if the capacity is large, the efficiency at the time of discarding is not good. The FIFO 13 is a static RA
M, etc., so the FIFO in the chip
This is also to reduce the area occupancy of the device.

The communication control unit 14 monitors the network and executes a communication process for sequentially sending and transmitting communication information stored in the FIFO 13 to the network. Based on the priority setting from the terminal device 2, the queue control unit 15 presents the token priority of the waiting data to the FIFO 13 on the transmission path via the communication control unit 14 or receives a token matching this. At this time, the communication controller 14 executes a process for causing the FIFO 13 to output standby data to the transmission path. Also, the queue control unit 15 adjusts the token priority and sends the end token to the communication control unit 14.
Through the transmission path again. At this time, depending on the processing content of the own station, there are cases in which the transmission path is desired to be used for communication with high priority, and cases in which the communication path may be opened to another station.

The data controller 16 generates an address corresponding to the pointer in the system memory 12 according to the pointer set by the CPU 11, reads out at least a part of data to be communicated from the system memory 12, and stores it in the FIFO 13. Data acquisition control for There are two types of pointers set therein, a high-priority pointer and a low-priority pointer. When a high-priority communication request occurs, the high-priority pointer is set and the low-priority pointer is set. May be returned to the initial value. In this case, the data control unit 16
The low-priority data waiting in the FIFO 13 is discarded, and the high-priority data is taken into the FIFO 13.

Next, the operation of the system configured as described above will be described with reference to the flowchart of FIG. (1) In the case of normal communication First, the CPU 11 sets a pointer (low priority) in the system memory 12 of data to be transmitted to the data control unit 16 (S1). That is, on the system memory 12, as shown in FIG. 4, data to be transmitted is stored in units of frames (packets), and a pointer to the next frame is added to the head of each frame. Therefore, the pointer initially set in the data control unit 16 becomes a pointer to the first frame, and thereafter, each time a frame is read, the next pointer is set, and these frames are chained and transmitted. . The CPU 11 sets the priority of the transmission data in the queue control unit 15 simultaneously with the setting of the pointer (S1).

Next, the data control section 16 outputs an address to the system memory 12 using the set pointer, and reads the data into the FIFO 13 (S2). If the data you want to send is long, read the first part. When the FIFO 13 is full, the queue control unit 15 waits for a signal indicating that transmission is possible from the communication control unit 14 (S3). When transmission becomes possible, the queue control unit 15 acts on the communication control unit 14 to cause the FIFO 13 to transmit the waiting data to the transmission path (S4). At the same time, it operates the data control unit 16 to move the next data to the FIFO 13 (S
2). The above operation is repeated until all data is transmitted.

(2) When a high-priority communication request is generated during communication When a high-priority communication request is generated while a low-priority frame is being transmitted (S5), the queue control unit 1
5, the priority is set, and a high-priority pointer is set in the data control unit 16 (S6). The queue control unit 15 waits until the transmission of the currently transmitted frame is completed (S7), and after the transmission is completed, executes the above-described processing of S2 to S4 on the high-priority data.

(3) When a high-priority communication request occurs before transmission (during standby) As described in step S3 of (1) above, a frame to be transmitted waits in the FIFO 13 until a transmission path becomes available. However, when a high-priority communication request occurs during this standby (separation between frames) (S5), first, a high-priority pointer of the data control unit 16 is set, and at the same time, the queue is set. The priority is also set in the control unit 15 (S
8). At this time, the low-priority pointer set in the data control unit 16 is returned to the pointer (initial value) indicating the low-priority frame currently waiting in the FIFO 13 (S8). Further, the data control unit 16 discards the data waiting in the FIFO 13 (S9), and stores the high-priority data in the F13.
It is stored in the IFO 13. Thereafter, the processing of steps S2 to S4 is repeated. Then, when the communication of the high-priority data is completed, the transmission process of the low-priority data is started again according to the low-priority pointer.

By performing such processing, transmission frames (packets) are continuously transmitted on the transmission path during normal communication, as shown in FIG. 5 (a). Also, as shown in FIG. 3B, when a high-priority communication request is made during the communication of one frame (b), the high-priority frame is transmitted after the completion of the communication of the frame. Therefore, the data is not cut off in the middle of the frame, and no abnormality occurs in the transmission path. Furthermore,
As shown in FIG. 11C, if a high-priority communication request occurs during the standby before the next frame B is transmitted after the transmission of one frame A is completed, the high priority Is transmitted preferentially. in this way,
In this system, the priority communication processing of high-priority data can be interrupted by appropriately performing data discard processing at the break of the data communication processing in the FIFO 13, and the storage area of the FIFO is effectively used. In addition, there is an advantage that a small-capacity FIFO can be used.

[0019]

As described above, according to the present invention,
When a communication request with a higher priority than the preceding communication request occurs, at the break of the communication process, the information related to the communication request with the higher priority is stored in the first-in first-out storage unit,
Since this high-priority communication request is processed with priority, there is no need to secure an extra storage area according to the priority, thereby improving the use efficiency of the memory and reducing the storage capacity. Since a high-priority communication request is processed at the break of the preceding communication process, incomplete data is not sent to the transmission path, and the transmission path is not damaged.

[Brief description of the drawings]

FIG. 1 is a block diagram of a communication control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a communication network using the communication control device.

FIG. 3 is a flowchart illustrating an operation of the communication control device.

FIG. 4 is a diagram showing a structure of transmission data on a system memory.

FIG. 5 is a time chart showing a state of priority control communication using the system of this embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Communication control device, 2 ... Terminal device, 3a-3c ... Station, 1
1 ... CPU, 12 ... System memory, 13 ... FIFO,
14: Communication control unit, 15: Queue control unit, 16: Data control unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H04L 29/06 H04L 13/00 305D (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/40 G06F 13 / 00 353 H04L 12/417 H04L 12/42 H04L 12/433 H04L 29/06

Claims (2)

(57) [Claims] 1. A communication control device for executing a communication process according to a plurality of types of communication requests having different priorities according to the plurality of types of communication requests. , A single-system first-in first-out storage means for storing at least a part of each of them, a communication control means for sequentially reading information stored in the first-in first-out storage means for communication processing, and a communication request having a higher priority than a preceding communication request. When communication occurs, it is determined based on the communication status of the communication control means whether the communication is currently being performed or is in a standby state. After processing the request and, if waiting, discard the waiting information in the first-in first-out storage means and process the high-priority communication request first, and then process the preceding communication request. A communication control device comprising: priority control means for processing. 2. When a communication request having a higher priority than a preceding communication request is generated, a pointer having the higher priority is set in the priority control means, and the first-in first-out storage is performed based on the set pointer. The communication control device according to claim 1 , wherein the communication control device is configured to be stored in the means.