JP2617601B2 - Bus control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus control device, and more particularly to a bus control device for giving a bus use right to a data transfer device in an information processing device of a bus structure communication system.

[Conventional technology]

Conventionally, as a control method of a bus use permission signal in this type of bus control device, there is the following method.

1. A method of sequentially selecting data transfer devices at fixed time intervals and granting the right to use the bus 2. Assigning a priority to each data transfer device and responding to a request from the data transfer device according to the priority [Problems to be Solved by the Invention] The former of the above-mentioned conventional bus control devices is provided with the right to use the bus irrespective of the presence or absence of a bus use request from the data transfer device, that is, Since the right to use the bus is also given to a data transfer device that has not requested use, in a system in which the bus use frequency and importance of the data transfer device are unbalanced, the bus of the data transfer device with a high demand for the bus is used. Use efficiency is reduced.

Further, the latter of the conventional bus control devices has a disadvantage that the data transfer device cannot issue the next request until the bus control device receives a bus use request signal from the data transfer device. Also, a signal response is required between the data transfer device and the selection circuit in the bus control device for priority determination, and during that time the bus cannot be used.
The use efficiency of the bus decreases.

[Means for solving the problem]

The bus control device according to the present invention includes: a unit connected to a plurality of data transfer devices via a data bus for giving priority to the data transfer devices; a counter provided corresponding to the data transfer device; Means for adding “1” to the counter when a data transfer request is issued from the device;
Means for selecting a data transfer device corresponding to a counter having a value equal to or more than "1" with reference to the value of the counter in accordance with a priority order; And means for permitting the data transfer device selected by the selection means to use the data bus.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

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

In FIG. 1, reference numeral 1 denotes a bus control device; 131 to 13n, counters for calculating the number of bus use requests in a use permission waiting state provided corresponding to the data transfer devices 21 to 2n; and 12, a counter 131 to 13n A priority determining circuit for determining a priority operation, 11 is a selecting circuit for selecting a counter from the priority determined by the priority determining circuit 12, and 14 is a bus permission for the data transfer device selected by the selecting circuit 11. A bus use permission signal generation circuit for generating signals, 15 is a data reception buffer, 21 to 2n are data transfer devices, 211 to 2n1 are data transmission circuits, and 212 to 2n2 are bus use request signal generation circuits for generating bus use request signals. Circuits, 213 to 2n3 are data transmission buffers, 214 to 2n4 are data transmission control circuits for controlling the data transmission buffers 214 to 2n4 when controlling data, 3 is a data bus, 41 to 4n are bus use request signals, and 51 to 4n. 5n is a bus Use permission signals 61 to 6n indicate counter subtraction signals for subtracting the counters 121 to 12n, respectively.

When a data bus use condition occurs in the data transmission circuits 211 to 21n, the data transfer devices 21 to 2n store the information in the data transmission buffers 213 to 2n3 and send a bus use request signal generation circuit 212 to the bus control device 1. The use of the data bus is requested by bus use request signals 41 to 4n from .about.2n2. In response to this request, "1" is added to the counters 121 to 12n.

The priority determining circuit 12 assigns priorities to the counters 121 to 12n in advance, and refers to each counter to make the priority of the counter having a value of “1” or more valid. The selection circuit 11 selects the counter having the highest priority with reference to the priority determination circuit 12 (it is assumed that 121 has been selected), and sends the corresponding data transfer device 21 a bus use permission signal generation circuit 14 A bus use permission signal 51 is generated.

The data transfer device 21 having received the bus use permission signal 51 transfers the contents of the data transmission buffer 213 to the data reception buffer 15 via the data bus 3 by the data transmission control circuit 214.

Further, the bus use permission signal generation circuit 14 decrements the counter 131 corresponding to the previously selected data transfer device 21 by "1", and ends the operation.

By the above operation, the counter 131 in the bus control device 1
13n store the number of data transfer requests from the data transfer devices 21 to 2n.Using this data, the priority determination circuit 12 and the selection circuit 11 perform priority determination including presence / absence of a request. can do. Further, since the number of bus use requests from each data transfer device is counted in the bus control device 1, the bus control device 1 can continuously send a bus use permission to the data transfer device. From here, a bus use request can be made without waiting for a bus use permission.

In FIG. 1, the data transfer is performed by the data transfer devices 21 to
Although the process is performed for the bus control device 1 from 2n, the reverse can be easily realized by the same method.

〔The invention's effect〕

As described above, according to the present invention, the bus control device has a counter for calculating the number of bus use requests for each data transfer device, so that the bus use is performed only for the data transfer device having the bus use request from each data transfer device. It is possible to permit the use of the bus and to select the data transfer device in parallel with the reception of the bus use request, so that a device with high bus use efficiency can be configured.

Further, since the counter in the bus control device holds the bus use request amount of the data transfer device, the data transfer device can report all occurrences of the bus use request, and the bus use request signal in the data transfer device can be reported. The generation circuit can be simplified.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Bus control device, 11 ... Selection circuit, 12 ... Priority determination circuit, 131-13n ... Counter, 14 ... Bus use permission signal generation circuit, 15 ... Data reception buffer, 21-2n ...
Data transfer device, 211-2n1 Data transmission circuit, 212-2
n2: Bus use request signal generation circuit, 213 to 2n3 ... Data transmission buffer, 214 to 2n4 ... Data transmission control circuit, 3 ...
... data bus.

Claims (1)

(57) [Claims] 1. A bus control device connected to a plurality of data transfer devices via a data bus, and in response to a data transfer request from the data transfer device, allowing the data transfer device to use the data bus. Means for retaining the priority of the data transfer device, a counter provided corresponding to the data transfer device, and means for adding "1" to the counter when a data transfer request is issued from the data transfer device; Means for selecting a data transfer device corresponding to a counter having a value equal to or more than "1" by referring to the value of the counter in accordance with a priority order; and selecting "1" from the counter corresponding to the data transfer device selected by the selection means. And a means for permitting the data transfer device selected by the selection means to use the data bus.