JPH04355862A - Common resource contention preventing circuit - Google Patents

Abstract

PURPOSE:To uniformly give the use right of a common resource to respective devices in a system for multiple relay of use requests to one common resource from plural devices. CONSTITUTION:Use requests to a shared resource 5 (bus 4) from devices 1 and 2 are prevented from contending by a repeater 6 and are inputted to a contention preventing circuit 7 together with the request from a device 3. The contention preventing circuit 7 selects one device, for example, the device 3 to permit it to use the common resource and sets a corresponding time slot of a bus use inhibiting signal 8 to the inhibiting state. Then, the device 3 cannot request the use of the common resource again. When another device 1 or 2 is permitted to use the common resource, a corresponding time slot of the bus use inhibiting signal 8 is set to the inhibiting state in the same manner. When all devices 1 to 3 terminate the use of the common resource 5 or do not use it for a certain time, the inhibiting states of all time slots of the bus use inhibiting signal 8 are released. Thus, all devices 1 to 3 uniformly obtain the use right of the common resource 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common resource conflict prevention circuit, and more particularly to a circuit that prevents common resource conflict when a plurality of devices use one common resource in a multi-stage configuration.

0002

2. Description of the Related Art Conventionally, this type of common resource contention prevention circuit has a plurality of devices 101, 102,
103 connects the common bus 4 to use the common resource 5.
connected via. Each of the devices 101 to 103 sends a bus use request signal 9a to use the common resource 5.
, 10a, 11a/bus use response signal 9b, 10b, 1
1b, and the devices that have received the response signal use the common resource 5 via the common bus 4. Bus use request/response signals are transmitted/received by devices 101 and 101, respectively.
102 is connected via the relay device 6 in consideration of electrical characteristics.
It is connected to the competition prevention circuit 107. Device 103 is directly connected to contention prevention circuit 107 . Relay device 106
includes a competition prevention circuit when simultaneous requests are made by the devices 101 and 102, and after selecting the two, it is connected to the competition prevention circuit 107 by a bus use request signal 12a and a bus use response signal 12b. In this configuration, the contention prevention circuit included in the relay device 6 and the contention prevention circuit 107 select the simultaneous use of common resources by the three devices 101 to 103 using a rotation priority method or the like.

0003

In this conventional common resource contention prevention circuit, when each device uses the bus at the same time, the probabilities of acquiring the right to use the bus are not the same for each device. In other words, in the configuration shown in FIG. 3, when the devices 101, 102, and 103 simultaneously request the use of the bus, when the contention prevention circuit included in the relay device 6 and the contention prevention circuit 107 are of the rotation priority system, the device 103 first requests the use of the bus. is allowed to use the bus, and then the relay device 6
The device 101 acquires the right to use the bus via the . The next person to acquire should be device 102, but if device 103 also requests use of the bus, contention prevention circuit 10
7 is a rotation-priority system, and therefore gives usage rights to the device 103. In this way, the device 103 has a probability of 5 for permission to use the bus.
Compared to 0%, devices 101 and 102 each have a probability of 25%.
Therefore, there was a problem that each device could not equally obtain permission to use the bus.

0004

[Means for Solving the Problems] A common resource conflict prevention circuit of the present invention is a common resource conflict prevention circuit for a system in which a plurality of devices use one common resource and a common resource usage request from each device is relayed in multiple stages. ;Each device that is permitted to use the common resource sends a disapproval signal indicating disapproval of a new common resource use request until all other devices use the common resource; a conflict prevention circuit that cancels the sending of the disallow signal to all of the devices when the device is unused for a preset time or more; and the conflict prevention circuit is provided in each of the devices; and a circuit for determining whether or not a request for use of the common resource is allowed based on the disallowance signal from the common resource.

[0005] In the above configuration, the disallow signal is sent to each time slot corresponding to each device on one signal line that commonly connects the contention prevention circuit and each device. The configuration can be set.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. Devices 1, 2, 3 are connected via a common bus 4 to use common resources 5. Each device 1~
3 are bus use request signals 9a, 10, 11a/bus use response signals 9b, 10b for using the common resource 5.
, 11b respectively, and the device that receives the response signal uses the common resource 5 via the common bus 4. Bus use request/response signals are transmitted/received by devices 1 and 1, respectively.
2 is connected to a competition prevention circuit 7 via a relay device 6 in consideration of electrical characteristics. The device 3 is directly connected to the anti-contention circuit 7. The relay device 6 includes a competition prevention circuit when devices 1 and 2 make simultaneous requests, and after selecting the two, sends bus use request/response signals 12a, 12b to the competition prevention circuit 7.
Connected by In this configuration, the contention prevention circuit included in the relay device 6 and the contention prevention circuit 7 select simultaneous use of the common resource by the three devices 1 to 3 using a rotation priority method or the like. Further, as shown in FIG. 2, the bus use disallow signal 8 includes a frame signal B indicating a frame break and a time slot in which one frame has more than the number of devices (for example, 4
) consists of a multiplexed signal A divided into This bus use disallow signal 8 is connected to each device 1 to 3, and the first three time slots of each time slot divided into four are used for each device 1.
It is supposed to indicate that use is not permitted for ~3. In this case, "1" is defined as permission, and "0" is defined as disallowance (unused time slots are always set to "1").

In this configuration, since devices 1, 2, and 3 use the common resource 5, if requests for use are issued at the same time, the conflict prevention circuit 7 selects one of them. in this case,
In the case of the device 3, the bus use disallowance signal 8 has the position of TS03 set to "0" as shown in signal A of FIG. When device 3 finishes using the bus, permission to use the next bus is given to the next device, that is, the device connected to relay device 6 from contention prevention circuit 7. In this case, it is assumed to be device 2. The bus use disabling signal 8 sets TS12 to "0" as shown in FIG. At this time, if device 3, which used the bus last time, requests to use the bus again, if the competition prevention circuit 7 uses the rotation priority system, the next device to be granted the right to use the bus will be device 3, not device 1. However, due to the bus use disallow signal 8 transmitted from the contention prevention circuit 7, the time slot TS1 of the device 3 used last time is
3 is 0, the device 3 that has detected this signal does not transmit the bus use request signal 11a. Therefore, since there is no request from the device 3, the competition prevention circuit 7 grants the usage right to the device 1. When all the time slots of the bus use disallowance signal 8 to each device are set to "0", that is, when all use rights are granted in response to a simultaneous use request, each time slot is set to "1" again. In addition, since not all devices 1 to 3 request use, even if some of the time slots defined for each device in the bus use disallow signal 8 are "1", no device can request use from any device for several frames. If there is no request for use, each time slot is set to "1" again.

[0009] In this way, the probability of acquiring the right to use the common resource when each device requests simultaneous use is equalized.

0010

As explained above, the present invention provides a system in which a plurality of devices use one common resource and a common resource use request from each device is relayed in multiple stages, in which the contention prevention circuit prevents the use of the common resource. For each permitted device, a disapproval signal indicating disapproval of new requests to use the common resource is sent until all other devices use the common resource, and the time during which the common resource is not used by all devices is set in advance. When the disallow signal continues for a specified period of time, the disallow signal to all devices is canceled, and each device determines whether or not to request the use of the common resource based on the disallow signal from the contention prevention circuit. This has the effect that common resources can be used equally by each device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram showing the contents of a bus use disallowance signal.

FIG. 3 is a block diagram showing an example of a conventional common resource contention prevention circuit.

[Explanation of symbols]

1, 2, 3, 101, 102, 103 device 4
Common bus 5 Common resource 6 Relay device 7, 107 Contention prevention circuit

Claims (2)

[Claims] Claim 1: In a common resource contention prevention circuit for a system in which a plurality of devices use one common resource and a common resource use request from each device is relayed in multiple stages; A disapproval signal indicating disapproval of a new common resource use request is sent until all the devices use the common resource, and the common resource is not used by all the devices for a preset time. a contention prevention circuit that releases the transmission of the disallowance signal to all of the devices when the above continues; and a contention prevention circuit that is provided in each of the devices and uses the common resource based on the disapproval signal from the contention prevention circuit. 1. A common resource conflict prevention circuit comprising: a circuit for determining whether a request is possible or not. 2. The disallowance signal is set for each time slot corresponding to each device on a single signal line that commonly connects the contention prevention circuit and each device. The common resource contention prevention circuit according to claim 1, characterized in that: