JPH10333793A - Bus interface circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To structure a bus interface which can use more than one function by itself without adding any dedicated signal by providing a common bus that functions use in common and a multipurpose bus which is usable differently by the functions, and physically providing a new dedicated bus interface by a selector circuit on a system side. SOLUTION: This circuit is equipped with the common bus 102 which is provided between an extension bus side and a system side and uses the functions on an extension bus side in common and the multipurpose bus 101 which is provided on the system side and usable differently by the functions. The selector circuit 11 selects and assigns one of a function bus 1 and a function bus 2 for actualizing different functions to the multipurpose bus 101 according to the contents of a select signal S1 supplied from the extension bus side. Consequently, the kind of the bus interface between the system side and extension bus side corresponding to the set function bus and all bus interfaces need not be provided unlike before.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus interface circuit, and more particularly to an extended bus interface circuit for a personal computer.

[0002]

2. Description of the Related Art In a conventional personal computer, an extended bus interface circuit has only one bus interface function. When a new function that needs to add a signal to the bus interface is added, In addition, a dedicated bus interface has been newly provided physically.

[0003]

Since the bus interface in the personal computer has only one bus interface function as described above, a new function that requires addition of a signal to the bus interface circuit is realized. If this is attempted, a new dedicated bus interface must be physically provided, which is wasteful and time-consuming.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and a plurality of functions can be provided with a single bus interface without physically providing a new dedicated bus interface. It is an object of the present invention to construct a bus interface circuit that can use the bus interface circuit.

[0005]

A bus interface circuit according to the present invention is used in common for a plurality of bus interfaces for realizing different functions, and is provided between a system side and an expansion bus side. And a plurality of function buses required for each function with respect to the plurality of bus interfaces, and a selector circuit for selecting any of the plurality of function buses and setting between the system side and the expansion bus side. It is characterized by having.

In this case, a plurality of function buses and a selector circuit are provided on the system side, and the selector circuit selects one of the plurality of function buses in response to a select signal supplied from the extension bus side to connect with the system side. It may be set between the extension bus side.

In the present invention configured as described above, the function bus selected by the selector circuit is set between the system side and the expansion bus side, and the function bus selected between the system side and the expansion bus side is set. The type of the bus interface depends on the set function bus, and it is not necessary to provide all the bus interfaces as in the related art.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention. The present embodiment is provided between the expansion bus side and the system side, and includes a common bus 102 that commonly uses a plurality of functions of the expansion bus side, and a multi-purpose bus that is provided on the system side and selectively used for each function. 101.

In FIG. 1, reference numeral 11 denotes a selector circuit, which selects one of a function bus 1 and a function bus 2 for realizing different functions according to the contents of a select signal S1 supplied from the extension bus side. And assign it to the multi-use bus 101.

Next, the operation of this embodiment will be described in detail with reference to FIG. 2 which is a circuit diagram showing the configuration of the selector circuit 11.

In FIG. 2, reference numeral 21 denotes an output buffer, which outputs a drive signal supplied from the function bus 1 to the multipurpose bus 101. An input buffer 22 outputs a drive signal supplied from the extension bus to the function bus 1. Reference numeral 23 denotes an inverter whose output terminal is connected to the output enable terminal of the output buffer 21 to operate the output buffer 21 and the input buffer 22 exclusively.

An output buffer 25 outputs a drive signal supplied from the function bus 2 to the multipurpose bus 101.
An input buffer 26 outputs a drive signal supplied from the extension bus to the function bus 2. Reference numeral 27 denotes an inverter whose output terminal is connected to the output enable terminal of the output buffer 25 so that the output buffer 25 and the input buffer 2
6 operate exclusively.

Reference numeral 24 denotes an AND circuit, which is a direction control signal S2 for the function bus 1 and a select signal S output from the extension bus.
1 to control the operation of the output buffer 21 and the input buffer 22 of the function bus 1.

Reference numeral 28 denotes an AND circuit, which is a direction control signal S3 for the function bus 2 and a select signal S output from the extension bus.
A signal obtained by inverting 1 by a 29 inverter is input, and the operation of the output buffer 25 and the input buffer 26 of the function bus 2 is controlled.

In the circuit configuration shown in FIG. 2, when an expansion bus adapter using the function bus 1 is mounted, a select signal is output from the expansion bus adapter. In the case of the present embodiment, the select signal S1 outputs "1" when the function bus 1 is used, and outputs "0" when the function bus 2 is used.

The select signal output from the expansion bus adapter is supplied to the A
The signal is input to the ND circuit 28. In addition, the direction control signal S2 of the function bus 1 which indicates an output when “1” and an input when “0” is input to the AND circuit 24,
The direction control signal S3 of the function bus 2 which indicates an output when "1" and indicates an input when "0" is input to the D circuit 28.

When the select signal S1 is "1" by the AND circuits 24 and 28 and the inverter 29, that is, when the function bus 1 is selected, the AND circuit 24 on the function bus 1 side is controlled by the direction control signal S2. Although the output value changes, the AND circuit 28 on the function bus 2 side outputs "0" unconditionally by the inverter 29 to enable the input buffer 26 and avoid collision of signals on the multi-purpose bus 101.

When the select signal S1 is "0",
That is, when the function bus 2 is selected, the function bus 2
The AND circuit 28 on the side is set to “1”
Is input, and the output value changes according to the direction control signal S3. However, since “0” is input to the AND circuit 24 on the function bus 1 side, “0” is unconditionally output and the input buffer 2
Enable 2 to avoid signal collisions on the busy bus.

FIG. 3 is a timing chart showing the operation of the circuit shown in FIG.

When the select signal S1 indicates "1", the function bus 2 maintains the input state, and the function bus 1
When the direction control signal S2 is "1", the output state is set, and when the direction control signal S2 is "0", the input state is set. Also,
When the select signal indicates “0”, the function bus 1 maintains the input state, and the function bus 2 outputs the direction control signal S of the function bus 2.
When 3 is "1", the direction control signal S3 becomes "
It becomes an input state when it is "0".

In this embodiment, the buses having different functions are switched by the selector circuit 11 as described above.
It is properly used as the multipurpose bus 101. In the above-described embodiment, the number of the function buses is two. However, the number of the function buses may be more. As the function bus selection circuit, various conventionally known techniques for selecting a circuit can be used. For example, each direction control signal output from each function bus is input, and a decoding circuit for selecting one of the input signals is used. , 22 (2
By outputting to the output enable terminals of (5, 26), a circuit for easily selecting a function bus can be easily obtained.

[0023]

Since the present invention is configured as described above, it has the following effects.

A selector bus that has a common bus used by a plurality of functions in common with a bus interface of a personal computer and a versatile bus that can be used for each function and switches a bus interface for each of a plurality of functions to the system side is newly provided. In order to physically provide a dedicated bus interface to a bus, a bus interface that can use a plurality of functions with one bus interface without adding a dedicated signal for each function on an interface board for an expansion bus is constructed. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing one embodiment of a bus sharing circuit of the present invention.

FIG. 2 is a diagram illustrating an internal configuration of a selector circuit in FIG. 1;

FIG. 3 is a timing chart showing an operation example of the circuit configuration of FIG. 2;

[Explanation of symbols]

 1, 2 function bus 11 selector circuit 21 output buffer 22 input buffer 23 inverter 24 AND circuit 25 output buffer 26 input buffer 27 inverter 28 AND circuit 29 inverter 101 common bus 102 multipurpose bus S1 select signal S2, S3 direction control signal

Claims (2)

[Claims] 1. A common bus which is commonly used for a plurality of bus interfaces for realizing different functions, and which is permanently provided between a system side and an expansion bus side; A bus interface circuit comprising: a plurality of required function buses; and a selector circuit for selecting any of the plurality of function buses and setting the selected bus between a system side and an expansion bus side. 2. The bus interface circuit according to claim 1, wherein a plurality of function buses and a selector circuit are provided on a system side, and said selector circuit is connected to a plurality of function buses in response to a select signal supplied from an expansion bus side. A bus interface circuit for selecting one of them and setting it between the system side and the expansion bus side.