RU2153775C1 - Method of access arbitration of group of users to common resources - Google Patents

Abstract

FIELD: radio engineering, realization of system of radio communication, radio control and computer hardware. SUBSTANCE: proposed method involves following sequence of operations: analysis of signals from each user with generation of decision on emergence of conflict situation, logic processing of signals and formation of signals permitting access of users to common resources with the aid of periodic bistable processor. EFFECT: simplified procedure of signal processing with use of simple means. 1 dwg

Description

 The invention relates to the field of radio engineering and can be used in computing systems, automation and control systems, radio communication systems, as well as in other fields of science and technology.

 In these systems, a situation always arises when through the so-called communication node (common resource) it is necessary to ensure the passage of more than one signal (from a group of subscribers).

 The absence of certain technical measures in this situation affects the quality of communication, its violation, leads to failures in management and a number of other unforeseen circumstances.

Among the various ways to solve this problem, three can be distinguished:
- prioritization of access;
- analysis of the temporal relationships of incoming signals;
- combined.

 The method of prioritizing access is most widespread.

 So in [1], a method is considered for improving the quality of service by assigning data priorities of numerous priorities (control identifiers) depending on the urgency of service and allowable data loss.

 In [2], the same problem is solved by setting the degree of urgency, which allows first of all to transmit the data that have the greatest urgency.

 In [3], a conflict situation is eliminated by coordinating access in accordance with the DEST or ST-2 (ST-3) standard.

 In the method for controlling several devices in a common data line [4], address generation is provided by a generator included in the control line. At rest, the generator is cycled over. With a simultaneous request for access to the line of several subscribers, the cyclic change of addresses stops when the readings of the address generator and the address of the subscriber among those who need access to the common line coincide, after which this subscriber is given access to the shared bus.

 The methods based on the analysis of temporal relationships when accessing the line can be attributed [5 and 6]. So in [5], for this purpose, network resource control signals are introduced, providing a change in the signal transmission rate depending on the degree of loading of the buffer memory of the switch. This method is based on the use of drives for temporary storage of data and means for calculating the necessary transfer rate.

 The method proposed in [6] provides cyclic sequential access to memory cells. The organization of time relationships in it is ensured by the intersection in time of the processes of writing and reading, which contributes to its more efficient use in the communication channel.

 It should be noted that the methods based on setting access priorities are easier to implement than the methods based on the analysis of time relationships, however, the use of the first somewhat degrades the efficiency of the communication channel by reducing the throughput.

 At the same time, methods based on the analysis of temporal ratios of received signals, despite their complexity of implementation, have little effect on the degradation of the bandwidth of the communication channel.

 Known combined access method used in dual-port RAM [7], the closest to the proposed and adopted as a prototype.

Using various types of arbitration to ensure high system performance, the prototype method with simultaneous access to shared resources (memory cells) of several subscribers includes the following sequence of operations:
- analysis of signals from each subscriber with the issuance of a decision on the occurrence of a conflict situation;
- logical processing of incoming signals with the subsequent issuance of permission signals for access to shared resources based on the arbitration algorithm.

 It should be noted that the analysis and logical processing procedures associated with the decision to access one of the subscribers to shared resources (memory cells) in this prototype are carried out in a rather complicated way using a large group of control signals and source data and a very complex organization of devices involved in the exercise of arbitration. Moreover, the arbitration process requires both hardware support inside the chip, and hardware or software support either from the subscribers themselves or from a specially organized arbiter.

 The prototype consists of an array of dual-port memory cells. Each port has autonomous control outputs: chip selection (CE), read or write permission (R / W), and output resolution (OE). These control pins allow independent read or write access to any memory location.

 To organize simultaneous writing / reading, the BUSY output is used. The presence of BUSY indicates that the port is trying to access the same location currently being accessed by another port.

 Two interrupt pins (INT) are used for port-to-port communications. The interrupt flag enables communication between ports or systems through a mailbox.

 To transmit a flag (marker) from one port to another, semaphores are used to ensure the distribution of resources between ports. The state of the semaphore indicates that the resource is in use. The semaphore logic is made up of eight public latches. Semaphore control is provided by two pins (SEM).

 Using the M / S pin ensures the functioning of the device as a master (master) (BUSY pins-outputs) or as a slave (slave) (BUSY pins-inputs).

 The aim of the invention is to simplify the arbitration procedure using simple means and expand the functionality.

 To achieve this goal, a method is proposed for arbitration of access of a group of subscribers to shared resources, including analysis of signals from each subscriber with a decision on the occurrence of a conflict and logical processing with the issuance of permission signals for access to shared resources.

 According to the invention, permission signals for access to shared resources are generated using a bistable batch process.

 The combination of distinctive features and properties of the proposed method from the literature are not known, therefore, it meets the criteria of novelty and inventive step.

 In FIG. 1 shows a block diagram of a device that implements the proposed method.

 In FIG. 2 shows the timing diagrams of the operation of the device.

 In FIG. 3 is a structural diagram of organizing access of N subscribers to shared resources.

The proposed method contains the following sequence of operations:
- analyze the signals from each subscriber with the issuance of a decision on the occurrence of a conflict situation;
- carry out logical processing and generate permission signals for access to shared resources using a bistable batch process.

 The essence of the proposed method of arbitration when several subscribers have access to shared resources is that when a conflict occurs, it is resolved by analyzing a periodic bi-stable process at the logical processing stage. For electronic circuits, this is the clock frequency.

The device (Fig. 1) that implements the proposed method for dual-port RAM contains: a two-channel logic processing block circuit, each of which contains a logical processing circuit 1 (2) and a ready signal shaper 3 (4), the fifth inputs of which are connected to the inputs the signals are BUSYI and BUSY2, and the outputs are the outputs of the device (the readiness signals of the RAM for the write / read cycle - RDY / BUSYI and RDY / BUSY2), and the comparator 5 (conditionally included in the dual-port RAM), the output of which is connected to the first inputs of the logic circuit Coy processing 1 (2) and inputs connected to address lines (SHA1, SHA2) of each channel (port). The input-output of the logic processing circuit 1 is connected to the input-output of the logic processing circuit 2. The output of the logic processing circuit 1 (2) of each channel is also connected to a dual-port RAM (modified write / read signals of RAM - WR _-1 and WR _-2 and modified signals samples of RAM ports - CS_ ₁ and CS_ ₂ ).

 The device inputs for each channel (port) are also the second, third and fourth inputs of logic processing circuit 1 (2), which are connected to the signals: write / read - WRI, WR2, port samples - CSI, CS2 and a periodic bi-stable signal CLK (clock frequency).

 The operation of the device that implements the proposed method is represented by the time diagram shown in FIG. 2.

In FIG. 2 shows the following types of signals:
CLK - clock signal;
ША1, ША2 - addressing signals;
WR - write / read signal;
CS - port fetch signal;
RDY / BUSY - readiness signal for completion of a write / read cycle
KT - signal from the output of the comparator;
WR_, CS_- modified write / read and port samples.

 As mentioned above, for the proposed arbitration of subscribers, when they both try to simultaneously write to the same memory location, an analysis of the batch process is necessary, which is the CLK signal. Its impact on the arbitration process can be easily seen from the timelines presented. Level 1 of the CLK signal prefers one subscriber, and level 0 prefers another. In this case, after the priorities are determined, the subscriber who received a lower priority gets access to the memory cell (bus) after the other subscriber completes the recording cycle to this cell.

The clock frequency (CLK) is selected for reasons of acceptable latency for the subscriber with a lower priority. The waiting time is determined by the inequality:
T _obsl ≤T _standby ≤T _obsl + T _CLK,
where T _ozh - waiting time,
T _obsl - period of the recording cycle of the subscriber who received the highest priority,
T _CLK - period of the clock frequency.

 In the absence of a conflict situation, each of the subscribers receives independent access to resources.

 It should be noted that the state of the CLK signal can influence the prioritization. So, for example, if both subscribers are synchronized from the CLK, then one of them will always have a higher priority (implementation of the method of prioritization). If the subscribers' clock frequencies differ from CLK, then the priorities of both subscribers will be equal and the probability of gaining access to shared resources first will be 0.5 for each of them, in case CLK is a meander (implementing a method for analyzing the timing of incoming signal ratios). If CLK is not a meander, the probability of accessing resources will be a function of the CLK duty cycle and, thus, probabilistic priorities (providing additional opportunities) can be provided.

 The considered method of access to resources can be implemented for the case when the number of subscribers is more than two.

 Consider the case of using a four-port RAM in accordance with the block diagram of the organization of access shown in FIG. 3.

 In this situation, all subscribers can be divided into six pairs, and for each pair, the circuit shown in FIG. 1. Thus, in this case, each subscriber can experience three conflict situations at once, the resolution of which will take place in turn by analyzing the state of the CLK signal.

 Conducted experimental studies on the layout of the device implemented by the proposed method, confirmed its advantage, based on the simplicity of the functional construction of simple and affordable elements.

 Currently, the proposed solution is used as a basic element in the creation of various signal processing devices.

The proposed method provides the following technical and economic effect:
- simplification of implementation through the use of simple elements;
- expansion of functionality.

Literature
1. Patent N 5487061, USA, "Providing priority services."

 2. Patent N 5535214, USA, "Processing requests for the transmission and reception of data in a multi-node network, taking into account their urgency."

 3. Application N 4407795, Germany, "Method and device for coordinating the access of multiple message sources to one bus."

 4. Application N 4326276, Germany, "A method for controlling multiple devices in a common data line."

 5. Application N 2301985, UK, "Management of cell flows in the ATM network."

 6. Copyright certificate N 1547031, USSR, "Buffer storage device".

 7. Cypress Semiconductor Corporation. Description of devices CY7C024 / 0241, CY7C025 / 0251 "Dual-Port Static RAM with Sem, Jnt, BuSY"

Claims (1)

 A method of arbitrating access of a group of subscribers to shared resources, including analysis of signals from each subscriber with a decision on the occurrence of a conflict situation and logical processing with the issuance of permission signals for access to shared resources, characterized in that permission signals for access to shared resources are generated using a bi-stable batch process.

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