JPH0227837A - Communication control system - Google Patents

Abstract

PURPOSE:To allow a specific node to acquire the transmission right with a larger rate than that of other nodes by providing a field representing the priority of an equipment to a token number and providing the communication control right to the specific equipment with priority. CONSTITUTION:A token control section 20 has a 2-bit switch as part of a token register 21 and the priority is decided by setting the switch. A token number received from a data bus 1 is stored in a token register 22, compared with the token number of the register 21 by a comparator 23, and when they are coincident, the equipment can send a data. If the data transmission is desired urgently and when the node during transmission at present has lower priority than itself, a dummy data is sent to cause data collision and to stop the data transmission of the opposite party, thereby fetching the transmission right. Thus, the transmission right is forcibly acquired from the node with lower priority than itself to attain data transmission.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a data bus communication control system. In particular, it relates to a communication control method for transferring data using a token method. [Prior Art] Conventionally, this type of communication control method has been used as shown in Fig. 3.
Assign a consecutive token number to each node. Then, each node acquires data transmission rights in the order of the assigned token numbers. Therefore, all nodes acquired the right to transmit data at the same rate. [Problems to be solved] In the conventional communication control method described above, as shown in Figure 3, token numbers are randomly assigned and each node obtains the right to transmit data at the same rate. It is not possible to obtain the transmission right at a higher rate than the node,
Furthermore, there is a problem in that when it is desired to transmit urgent data, transmission rights cannot be obtained. For this reason, a problem arises in that nodes that require frequent data transfer, such as the host CPU, and nodes that need to transfer data while maintaining real-time performance cannot freely transfer data. was there. The present invention has been made in view of the above-mentioned problems.
The purpose of the present invention is to provide a communication control method that allows a specific node to obtain transmission rights at a higher rate than other nodes. [Means for solving problem H] In order to achieve the above object, the present invention provides a bus system in which data transfer is controlled using a token system, in which a device prioritizes a token number instead of a continuous series of token numbers. By providing a field indicating the rank, a specific device is given preferential communication control authority.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. The first III is block e2. of the communication control method according to the present invention.
This is a diagram. The communication control method in this embodiment is characterized by defining some bits of the conventional token number as special bits for determining a specific device group, and by using these special bits, priority can be determined. It has the ability to allocate a high-priority token number to a node that requires it. This will be explained in detail below. The communication control system according to the present invention is a bus interface unit that interfaces with the data fist bus l! O, Token rvI control 7IIz that performs control regarding tokens
o, and a data transmission/reception control section 30 that transmits and receives data between the data bus 1 and the CPU/terminal device. The token control unit 20 includes an allocation token register 21 for storing an allocated token number, a receiving token register 22 for storing a received token number from the data bus, a comparator 23 for comparing the 1 allocated token and the received token, and a group. Groupby to process bits? ) Processor 24° and data non-transmittal @ (Bus Time
It is composed of a BTO detector 25 that detects Out:BTO). Each *a has 2 bl t switches as -aB of the 1 allocation token register 21, and the priority order is determined by the setting of this space. Devices in which the switch setting is 00 become a group with a high priority. at initialization. Each device gets a token number, but the upper two bits are assigned as group bits, so the lower two bits are assigned as group bits.
Only Bifu and To are randomly determined. An example of token number assignment is shown in FIG. The token number received on the data bus is also. It is stored in the token register 22 and compared with the token number in the allocated token register 21 by the comparator 23. If the token numbers match, the device can transmit data. Normally, the transmission right is acquired in descending order of the assigned token number and data is transmitted. In the example in Figure 2, oo
oo→0001→(BTO)→0100→0101 Pass(
BTO) → 1000 → tool-(BTO) → (BT
O) Control is performed in the order of →0000-... In this case, the next one after 0001 is 0010, but 0010
Since there is no BTO, a BTO occurs. BTO detector 25 is B
When TO is detected, the node with serial number 00 of the group with the next highest priority after the group at that time acquires the transmission right. Then, when BTO occurs twice in a row, oo
Node oo acquires the transmission right. If you want to send data urgently, if the group of the node that currently has the right to send has a lower priority than the group to which you belong, send dummy data and force 1 collision (data collision), causing the other party's data transmission to stop, stealing the transmission right, and then outputting the data that the other party wants to send. The other party with whom the collision occurred is assigned another token number again, and transmits data at that time. [Effect of the Invention] As explained above, the present invention sets a group bit in the token number and identifies the bit, so that if the currently transmitting node has a lower priority than itself, the This has the effect that it is possible to acquire transmission rights and perform data transfer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the communication control method according to the present invention, FIG. 2 is a diagram showing an example of token number assignment according to this embodiment, and FIG. 3 is a diagram showing an example of conventional token number assignment. . :Bus interface unit Nidokun control unit:Assignment token register:Receiving token register:Comparator Nigel loop bit processor:BTO detector:Data transmission/reception control unit

Claims (1)

[Claims] A bus that uses a token method to control data transfer.
A communication control method characterized in that, in a system, a field indicating device priority is provided in a token number to give preferential communication control rights to a specific device.