JPH01208855A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To assure test mode switching when there is no dead terminal by switching signal terminal by an output from a monostable multivibrator which is actuated by an output from a rectifier connected to a power supply input terminal through a capacitor. CONSTITUTION:Once an alternating signal is applied from an external alternating power supply 2 to a power supply input terminal 3 through an external capacitor 10, the signal is differentiated by a capacitor 5 and rectified through a diode 6 to actuate a monostable multivibrator 7. The monostable multivibrator 7 sustains its high level output for a predetermined time interval as it receives an input signal while sustaining without interruption the high level output whilst there is an input continuously. When the monostable multivibrator 7 has its high level output, AND circuits 8, 9 effect test mode switching. Hereby, a test signal from the signal input terminal 4 is fed to a testing circuit through the AND circuit 9 which ANDs the output from the monostable multivibrator 7 and the input signal from the signal input terminal 4.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to semiconductor integrated circuits.

[Conventional technology]

In conventional semiconductor integrated circuits, when switching to a test mode, an empty terminal is used as a test mode switching instruction terminal.

[Problem that the invention seeks to solve]

The above-mentioned conventional semiconductor integrated circuit uses an empty terminal as a test mode switching instruction terminal, so there is a drawback that the test mode cannot be changed if there is no empty terminal.

[Means for solving problems]

The semiconductor integrated circuit of the present invention includes a rectifier circuit that is connected to a power input terminal via a capacitor and rectifies an alternating current signal when an alternating current signal is applied to the power input terminal, and a rectifier circuit that is activated by the output of the rectifier circuit for a predetermined period of time. It is configured to include a monostable multivibrator that generates a continuous output, and a switching circuit that switches a signal terminal to a test mode switching designation terminal based on the output of the monostable multivibrator.

〔Example〕

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.

As shown in FIG. 1, a capacitor 5 is connected to the power input terminal 3 of the semiconductor integrated circuit 1, and an external AC power source 2
When an AC signal is applied to the power input terminal 3 via the external capacitor 10, it becomes a differential signal at the capacitor 5,
It is rectified by a diode 6 and activates a monostable multi-vib break 7.

The monostable multivibrator 7 maintains a high level output for a certain period of time when there is an input signal, and continues to output a high level while there is a continuous input signal. AND circuits 8 and 9 as switching circuits by the output of monostable multivibrator 7
The test mode is switched by .

The AND circuit 8 takes the logical product of the inverted signal of the output of the monostable multivibrator 7 and the input signal from the signal input terminal 4, and the AND circuit 9 takes the logical product of the output of the monostable multivibrator 7 and the input signal from the signal input terminal 4. The configuration is to take the logical product of .

Therefore, when the output of the monostable multivibrator 7 is at a low level, the input signal from the signal input terminal 4 is supplied to the original circuit (not shown) through the AND circuit 8, and the output of the monostable multivibrator 7 is at a high level. In this case, the signal input from the signal input terminal 4 is supplied to a test circuit (not shown) through the AND circuit 9. However, in the test mode, the dest signal is input to the signal input terminal 4.

As described above, although the signal input terminal is used in the explanation of the embodiment, the present invention can also be applied to the case of a signal output terminal.

〔Effect of the invention〕

As explained above, the present invention includes a rectifier, a monostable multivibrator, and a switching circuit connected to a power input terminal via a capacitor, and applies an AC signal to the power input terminal to instruct the signal terminal to switch to a test mode. By using it as a terminal, there is an effect that the test mode can be switched even when there is no empty terminal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. 1... Semiconductor integrated circuit, 2... AC power supply, 3...
Power input terminal, 4... Signal input terminal, 5... Capacitor, 6... Diode, 7... Monostable multi-by-break, 8, 9... AND circuit, 10... Capacitor.

Claims (1)

[Claims] A rectifier circuit that is connected to a power input terminal via a capacitor and rectifies an AC signal when an AC signal is applied to the power input terminal, and a monostable that is activated by the output of the rectifier circuit and generates an output that continues for a predetermined time. A semiconductor integrated circuit comprising: a multivibrator; and a switching circuit that switches a signal terminal to a test mode switching designation terminal based on the output of the monostable multivibrator.