JPH02277347A - Two-way bus test circuit - Google Patents

Abstract

PURPOSE:To conduct the test of a 2-way bus without operating an internal circuit of an LSI by disconnecting the 2-way bus from the internal circuit when a test signal is received and connecting the 2-way bus to a 2-way test bus gate section. CONSTITUTION:Internal circuit disconnecting sections 3a-3c receive a test start signal via a test terminal 6a to disconnect an LSI internal circuit 8 from 2-way buses 9a-9c. Then a direction control section 2a receives a direction switching signal via a test terminal 6b and sends the signal to direction control sections 2b, 2c. The direction control sections 2b, 2c receive the signal to switch the destination of the signal to apply direction control of gate sections 10a-10f connecting to the 2-way buses 9a-9c from a conventional LSI circuit 8 to the direction control section 2a. Thus, the LSI circuit 8 is disconnected at the test.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bidirectional bus test circuit that easily tests an LSI having a bidirectional bus.

[Conventional technology]

As logic circuits become more highly integrated, their testing becomes increasingly difficult. Conventionally, as a test facilitation technique for LSI sequential circuits, a scan scan method has been used that operates a flip-flop in the circuit as a shift register during testing, sets a test vector, and extracts a state vector after normal operation for one clock. The method has been put into practical use. Usually, LSIs having bidirectional buses are tested using this method.

[Problem to be solved by the invention]

In the conventional scan path method mentioned above, mainly LSI
Since the main focus is on testing the internal circuits of the LSI, this method is not appropriate if you want to mainly check the electronic circuit panels on which the LSI is mounted and the connections between the electronic circuit panels. . In particular, L with a bidirectional bus
When performing a connection test between an electronic circuit panel on which an SI is mounted and the electronic circuit panels, it is necessary to create test data for operating the internal circuits of the LSI in order to control the bidirectional bus. Therefore, it has the drawback of requiring a large amount of man-hours and a high technical level.

An object of the present invention is to provide a bidirectional bus test circuit that can test an electronic circuit panel equipped with an LSI having a bidirectional bus without operating the internal circuits of the LSI. There is a particular thing.

[Means to solve the problem]

The bidirectional bus test circuit of the present invention is suitable for bidirectional buses and LSI
In a bidirectional bus test circuit installed in an LSI that has an internal circuit that functions, there is a direction control section that receives a switching signal and controls the direction of data transfer, and a bidirectional bus that opens and closes a gate under the control of the direction control section. a test bus gate section; a disconnection section that receives a test signal and disconnects the bidirectional bus from the internal circuit; and two devices connected between the separated bidirectional buses via the bidirectional test bus gate section. It is configured with a test lotus for the test.

〔Example〕

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

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

The LSII shown in FIG. 1 has bidirectional bus terminals 7a to 7c.
In addition to the LSI internal circuit 8 that makes the LSI function, the bidirectional buses 9a to 9C, and the gate sections 10a to 10f connected to the bidirectional buses 9a to 9C, the LSI receives a new switching signal and determines the direction of data transfer. direction control units 2a to 2C, which control the direction control units 2a to 2C, bidirectional test bus gate units 5a to 5f, which open and close gates under the control of the direction control units 2a to 2C, and bidirectional test bus gate units 5a to 5f, which receive test signals and control the bidirectional buses 9a to 9C inside the LSI. The test information signal is relay-connected to the disconnection sections 3a to 3C disconnected from the circuit 8 and the bidirectional test bus 4 connected between the disconnected bidirectional buses via the bidirectional test bus gate sections 5a to 5f. It has test terminals 6a6b.

Although a plurality of bidirectional bus terminals 7a to 7c, test terminals 6b, and bidirectional test bus 4 are normally provided, only one is shown in this example.

Testing of an LSII having bidirectional buses 9a to 9c is performed as follows.

First, the internal circuit disconnection parts 3a to 3C are connected to the test terminal 6a.
A test start signal is received via the LSI internal circuit 8, and the LSI internal circuit 8 is disconnected from the bidirectional buses 9a to 9C.

Next, the direction control section 2a receives the direction switching signal via the test terminal 6b, controls the direction of the bidirectional test bus gate sections 5a to 5f, and transmits this signal to the direction control sections 2b and 2c. By receiving the test start signal, the direction control units 2b and 2c change the reception destination of the signal for controlling the direction of the gate units 10a to 10f connected to the bidirectional buses 9a to 9c to the normal LSI internal circuit 8. The direction control unit 2a is switched from the direction control unit 2a to the direction control unit 2a. In this way, the bidirectional buses 9a to 9c are connected to each other via the bidirectional test bus 4 without operating the LSI internal circuit 8, and the bidirectional bus terminal 7a is connected to the bidirectional bus terminal 7a.
Data is sent and received between 7c and 7c.

Therefore, L with bidirectional buses within the same electronic circuit panel
Applying this method to other LSIs equipped with SI, L
A bidirectional bus can be tested without operating the internal circuits of the SI, and connections between electronic circuit panels can be tested.

〔Effect of the invention〕

As explained above, the present invention provides L
When testing electronic circuit panels equipped with SI, LS
Since it is possible to easily test the bidirectional bus without operating the internal circuit of the IC, it is not necessary to have a high technical level to fully understand the original functional operation of the LSI, and it is also possible to test the electronic circuit panel. This has the effect of significantly reducing the number of man-hours required to create data.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an LSI according to an embodiment of the present invention. 1... LSI, 2a to 2C... Direction control section, 3a to 3C... Separation section, 4...
・Bidirectional test bus, 5a to 5f...Bidirectional test bus skate section, 6a, 6b...Test terminal, 7a to 7c
...Bidirectional bus terminal, 8...LSI internal circuit, 9a-9c...Bidirectional bus, 10a-10
f...Gate part.

Claims (1)

[Claims] LS with bidirectional bus and internal circuit to function LSI
In the bidirectional bus test circuit provided in I, a direction control section receives a switching signal and controls the direction of data transfer, a bidirectional test bus gate section opens and closes a gate under control of the direction control section, and a test A disconnection unit that receives a signal and disconnects the bidirectional bus from the internal circuit, and a bidirectional test bus connected between the disconnected bidirectional buses via the bidirectional test bus gate unit. A bidirectional bus test circuit characterized by: