JP2737179B2 - Bus system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for an information processing apparatus. In particular, the present invention relates to control of a bus use right of a bus control device.

〔Overview〕

In the present invention, a plurality of user devices are connected to one bus,
In a bus system for controlling the priority, a control circuit for controlling the priority switching and a priority determination switching circuit for rewriting the priority by the control circuit are provided, and the priority is switched according to a priority change request from a user device. By rewriting, the bus use priority order of a plurality of user devices can be easily changed from the user device side, and the processing efficiency can be improved.

[Conventional technology]

When a plurality of user devices are connected to one bus and a bus use request is issued from the plurality of user devices, one of the plurality of user devices is selected to allow the user device to use the bus. Is required.

Conventionally, such control is performed by providing a bus control device for controlling a bus in a bus system, transmitting a bus request signal for requesting bus use from each user device, and permitting the bus use from the bus control device. This is performed by sending a bus acknowledge signal to the user equipment. When a bus request signal is sent from a plurality of user devices, the bus control device follows a predetermined priority order,
The bus acknowledgment signal is sent to the user device having the highest priority from among the bus request signals sent to give the right to use the bus.

[Problems to be solved by the invention]

The prior art bus control device described above has a drawback that priorities for bus requests are determined in advance, so that if the priority of bus use of the user device changes due to processing, processing cannot be performed efficiently.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus capable of efficiently performing processing even when the priority order of bus use of a user apparatus changes.

[Means for solving the problem]

The present invention includes a plurality of user devices, a bus to which the plurality of user devices are connected, and a bus control device for controlling a right to use the bus, wherein the bus control device includes the plurality of user devices in advance. A bus system including a priority determination switching circuit in which the priority order of bus use is set, and a control circuit for granting the right to use the bus according to the priority in response to a bus request signal from each user device, The user apparatus further includes means for transmitting a specific logical value to a hardware status signal when requesting bus use preferentially, wherein the control circuit is configured to perform the control when the hardware status signal includes the specific logical value. The apparatus further comprises means for granting a bus use right to the user apparatus transmitting the specific logical value regardless of the priority order.

When the specific logical value is transmitted to the hardware status signal from a plurality of user devices, a new priority may be set in the order of the transmission start timing.

[Action]

Normally, when a user device uses a bus, when a bus request signal requesting use of the bus is sent from the user device that wants to use the bus to the bus control device, the bus control signal is used to give priority to the bus control device. A bus acknowledgment signal indicating permission to use the bus is sent to the highest user device to grant the right to use the bus.

However, there may be a case where a user device having a low priority order wants to use the bus preferentially. In such a case, when the user device outputs a hardware status signal to the control circuit of the bus control device, the control circuit receiving the signal changes the priority by controlling the priority determination circuit. As a result, the processing can be efficiently executed in accordance with the situation.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

The embodiment of the present invention includes a plurality of user devices 1, 2, 3 and a bus 10 to which the plurality of user devices 1, 2, 3 are connected.
A bus control device 4 for controlling the right to use the bus 10. The bus control device 4 includes a priority determination switching circuit 41 in which priorities of bus use are set in advance for a plurality of user devices 1, 2 and 3. And a control circuit 42 for granting the right to use the bus 10 according to the priority in response to the bus request signals 11, 21, 31 from each of the user devices 1, 2, 3; Includes a means for transmitting a specific logical value to the hardware status signals 13, 23, and 33 when requesting bus use preferentially, and the control circuit 42 transmits the specific logical value to the hardware status signals 13, 23, and 33. Means for granting the right to use the bus to the user devices 1, 2, and 3 transmitting the specific theoretical value when there is a value, regardless of the priority.

The operation of the embodiment of the present invention thus configured will be described.

Here, it is assumed that the user devices 1, 2, and 3 have higher priorities in this order. When the user devices 1, 2, and 3 want to use the bus, they send the bus request signals 11, 21, and 31 to the bus control device 4 based on the theory 1 respectively. Upon receiving this signal, the bus control device 4 sends the bus acknowledge signal 12 as a logical 1 to the user device 1 having the highest priority, and gives the user device 1 permission to use the bus.

If the user device 3 with a lower priority wants to use the bus preferentially, the hardware status signal 33 is set to logic 1 and the bus request signal 31 is set to logic 1. At this time, even if the other user devices 1 and 2 set the bus request signals 11 and 21 to logic 1, if the hardware status signals 13 and 23 are not at logic 1, the priority order is the user device 3,
The priority determination switching circuit 41 makes a determination through the control circuit 42 in the order of 1 and 2, and the bus control device 4 sends a bus acknowledge signal to give the user device 3 permission to use the bus.
Let 32 be logic one.

When specific logic values are transmitted to the hardware status signals 13, 23, and 33 from the plurality of user devices 1, 2, and 3, new priorities are set in the order of the transmission start timings.
By changing the priority of each of the user devices 1, 2 and 3 as described above, the bus can be used efficiently.

〔The invention's effect〕

As described above, according to the present invention, the bus control device is provided with the priority determination circuit and the control circuit controlled by the hardware status signal from the user device in the bus system, so that the bus usage of a plurality of user devices can be achieved. Can be changed by processing, and the bus can be used efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. 1, 2, 3 ... user device, 4 ... bus control device, 11,
21, 31, bus request signal, 12, 22, 32, bus acknowledge signal, 13, 23, 33, hardware status signal, 41, priority determination switching circuit, 42, control circuit.

Claims (1)

(57) [Claims] A plurality of user devices; a bus to which the plurality of user devices are connected; and a bus control device for controlling a right to use the bus, wherein the bus control device includes a plurality of user devices in advance. A bus system comprising: a priority determination switching circuit in which a bus use priority is set for a device; and a control circuit for giving a bus use right in accordance with the priority in response to a bus request signal from each user device. Wherein the user device includes means for transmitting a specific logical value to a hardware status signal when requesting bus use preferentially, and the control circuit is configured to control when the specific logical value is present in the hardware status signal. Regardless of the priority, the hardware status signal of the specific logical value is transmitted to the user device transmitting the specific logical value in the order of timing. A bus system comprising means for setting a new priority and granting a right to use the bus.