JPH04188760A - Semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To control and observe an internal signal under a test state without increasing the propagation time of the internal signal under a normal working state by adding a means, in which an output from a gate circuit is brought to a high impedance state (a Z state), and a switching circuit. CONSTITUTION:A means 7, in which a gate circuit C is brought to a Z state, a means 8, in which other signals are transmitted over the output node of the gate circuit C when an output from the gate circuit C is brought to the Z state, and a switching means 6, in which the output signal 2 of a circuit block A is transmitted over a gate circuit except the gate circuit C or a terminal when the output from the gate circuit C is brought to the Z state, are provided. Consequently, when the gate circuit C is brought to the Z state, the input signal 4 of a circuit block B can be controlled form the outside, and the output signal 2 of the circuit block A can be observed on the outside. Accordingly, an internal signal can be controlled and observed under a test state without increasing the propagation time of the internal signal under a normal working state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor integrated circuit device having a gate circuit having at least one input and one output.

[Prior art] In the conventional technology, when testing a semiconductor integrated circuit device that has a circuit block A and a circuit block B as shown in FIG. 1, the output of circuit block A is input to circuit block B. In order to easily control the input signal of circuit block B from the outside, a selection circuit 3 shown in FIG. 2 was added.

This selection circuit 3 has a function of selecting either the output signal 7 of the circuit block A or the signal 4 from the outside according to the control signal 5 and inputting the selected signal to the circuit block B. In the normal use state, the signal 7 is transmitted to the circuit block B, and when the logic opposite to the normal use state is input to the control signal 5 (hereinafter referred to as the test state), the signal 4 from the outside is transmitted to the circuit block B. tell.

Further, in order to observe the output of the circuit block A in the test state, an observation signal wiring 6 was added.

[Problems to be Solved by the Invention] However, by adding the selection circuit 3 as shown in FIG. 2, the propagation time of the signal 7 in the normal usage state increases by the response time of the selection circuit 3. It had the problem of being stored away.

Furthermore, by adding the signal distribution g6 to observe the signal 7, there is a problem in that the capacitance between the wiring and the 1i source increases and the propagation time of the signal 7 increases.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a semiconductor integrated circuit device with a simple configuration that can control and observe internal signals in a test state without increasing the propagation time of internal signals even in a normal use state.

[Means for Solving the Problems] A semiconductor integrated circuit device of the present invention includes a) a semiconductor integrated circuit device having a gate circuit having at least one input and an output, and b) an output of the gate circuit in a Z state. C) means for transmitting another signal to the output node of the gate circuit when the output of the gate circuit is in the Z state; d) means for transmitting another signal to the output node of the gate circuit when the output of the gate circuit is in the Z state; The present invention is characterized in that it has means for transmitting the input signal to a gate circuit other than the gate circuit or a terminal.

[Operation] In the gate circuit of the semiconductor integrated circuit device configured as described above, an external signal can be transmitted to the pressure of the gate circuit by setting the output of the gate circuit to the Z state. Further, when the output of the gate circuit is in the Z state, the input signal of the gate circuit can be observed externally.

[Example〕 The present invention will be described below based on examples.

Figure 3 shows a general circuit that has circuit block A, circuit block B, and gate circuit C, and the output of circuit block A is input to gate circuit C, and the output of gate circuit C is input to circuit block B. It is a semiconductor integrated circuit device.

FIG. 4 shows a semiconductor integrated circuit device of the present invention, in which the semiconductor integrated circuit device of FIG. means 8 for transmitting another signal to the output node of gate circuit C, and means 6 for transmitting output signal 2 of circuit block A to a gate circuit other than gate circuit C or to a terminal when the output of gate circuit C is in Z state. This is what I did.

When testing the semiconductor integrated circuit device shown in FIG. 3, when the gate circuit C is in the Z state, the input signal 4 of the circuit block B is externally controlled by the semiconductor integrated circuit device of the present invention shown in FIG. This also makes it possible to observe the output signal 2 of the circuit block A externally.

FIG. 5 is an example of a semiconductor integrated circuit device of the present invention using MOS transistors.

1 is a circuit block A, 2 is a circuit block B, 3 is an inverter circuit, 4 is a switch circuit that puts the inverter circuit 3 into the Z state, 5 and 6 are switch circuits, 7 is a control signal for the switch circuit, 8 is a control signal to the outside The observation signal 9 is an external control signal.

When the control signal 7 of the switch circuit is in the low level test state, the inverter circuit 3 is in the Z state and the switch circuits 5 and 6 are turned on. At this time, the circuit block B can be controlled by an external control signal 9, and the output signal of the circuit block A can be observed by an external observation signal 8.

When the control signal 7 of the switch circuit is at a high level during normal use, the inverter circuit 3 functions as an inverter, and the switch circuits 5 and 6 are turned off. At this time, by turning off switch circuits 5 and 6, the external observation signal 8 and external control signal 9 are not affected at all, so the signal propagation time from circuit block A to circuit block B is There is no increase compared to the case of a normal circuit without circuit 4.5.6.

[Effects of the Invention] As explained above, the semiconductor integrated circuit device of the present invention has the following effects:
The simple configuration of adding a switch circuit makes it possible to control and observe internal signals in a test state without increasing the propagation time of internal signals even in a normal use state.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a portion of a conventional semiconductor integrated circuit device. 1...Circuit block A 2...Circuit block B FIG. 2 is a block diagram in which a selection circuit is added to FIG. 1. 1...Circuit block A 2...Circuit block B 3...Selection circuit 4...Signal from outside 5...Control signal for selection circuit 6...Observation signal wiring 7...Circuit Output signal of block A FIG. 3 is a block diagram of a portion of a semiconductor integrated circuit device having a conventional gate circuit. 1...Circuit block A 2...Output signal of circuit block A 3...Gate circuit C 4...Input signal of circuit block B 5...Circuit block B FIG. 4 shows the implementation of the present invention FIG. 1 is a block diagram of an example semiconductor integrated circuit device. 1...Circuit block A 2...Output signal of circuit block A 3...Gate circuit C 4...Input signal of circuit block B 5...Circuit block B 6...Output to circuit block Means 7 for transmitting signal 2 to a gate circuit or terminal other than gate circuit C... Means 8 for putting gate circuit C into two states... Means for transmitting another signal to the output node of gate circuit C FIG. FIG. 1 is a circuit diagram of a semiconductor integrated circuit device using a MOS transistor according to an embodiment of the present invention. 1...Circuit block A 2...Circuit block B 3...Inverter circuit 4...Switch circuit 5゛...Switch circuit 6...Switch circuit 7...・Switch circuit control signal 8...Observation signal to the outside 9...Control signal from the outside Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (1 person) Figure 2

Claims (1)

[Scope of Claims] a) A semiconductor integrated circuit device having a gate circuit having at least one input and one output, b) means for bringing the output of the gate circuit into a high impedance state (hereinafter referred to as Z state); c) means for transmitting another signal to the output node of the gate circuit when the output of the gate circuit is in the Z state; and d) means for transmitting another signal to the output node of the gate circuit when the output of the gate circuit is in the Z state. A semiconductor integrated circuit device comprising means for transmitting data to a gate circuit or terminal other than the gate circuit.