JPH04303274A - One-chip microcomputer - Google Patents

Abstract

PURPOSE:To suppress the transmission of noise generated in a system bus I/O circuit to an internal circuit as little as possible, to prevent the generation of malfunction and to obtain a highly reliable one-chip microcomputer. CONSTITUTION:The power supply metallic wiring 11 of the system bus I/O circuit 3 and the power supply wiring 10 of the internal circuit 2 are respectively wired and the ground metallic wirings 13, 12 of respective circuits 3, 2 are also respectively wired. In addition, the power supply terminals 6, 5 of respective circuits 3, 2 are respectively provided and the ground terminals 9, 8 of respective circuits 3, 2 are also respectively provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-chip microcomputer that processes data, and more particularly to power supply wiring and power supply terminals for a built-in system bus input/output circuit.

0002

2. Description of the Related Art FIG. 2 is a block diagram of a conventional one-chip microcomputer. In FIG. 2, 1 is a chip of a one-chip microcomputer, 2 is an internal circuit provided in chip 1 other than the system bus input/output circuit, 3 is the system bus input/output circuit that inputs and outputs data, and 4 is an internal circuit. Metal wiring for supplying power to the circuit 2 and the system bus input/output circuit 3, 5 and 6 are power supply terminals connected to the metal wiring 4, and 7 supplies a ground potential to the internal circuit 2 and the system bus input/output circuit 5. Metal wiring for, 8,
9 is a ground terminal connected to the metal wiring 7.

As described above, in the conventional one-chip microcomputer, the power wiring and ground wiring of the internal circuit 2 and the power wiring and ground wiring of the system bus input/output circuit 3 are connected to the metal wiring 4 and the metal wiring 7 inside the chip 1.
are connected by.

0004

[Problems to be Solved by the Invention] Currently, the speed of one bus machine cycle of one-chip microcomputers has increased to several hundred ns, and the bit length of data handled has increased to 4 bits, 8 bits, 16 bits, and 32 bits. Because of this, when the system bus changes many bits at once, noise may be applied to the power supply or ground, potentially causing malfunctions in internal circuits. In addition, a one-chip microcomputer has various peripheral function circuits in addition to the CPU as an internal circuit, but the signal period generated by the peripheral function circuits is at most μs to m.
Moreover, it is extremely rare for the signals of a large number of signal lines to change at once, such as in a system bus. Therefore, in conventional one-chip microcomputers, noise generated particularly in the system bus input/output circuit is the main cause of malfunctions in the internal circuits.

The present invention was made to solve the above-mentioned problems, and provides a one-chip microcomputer that can minimize the transmission of noise generated in the system bus input/output circuit to internal circuits and prevent malfunctions. The purpose is to provide

[0006]

[Means for Solving the Problems] A one-chip microcomputer according to the present invention has a system bus input/output circuit 3.
The power supply wiring and ground wiring of the internal circuit 2 and the power supply wiring and ground wiring of the internal circuit 2 are wired separately, and the power supply terminal and ground terminal of the system bus input/output circuit 3 and the power supply terminal and ground terminal of the internal circuit 2 are separately wired. It was established in

[0007]

[Operation] The power supply wiring and ground wiring of the system bus input/output circuit 3 and the power supply wiring and ground wiring of the internal circuit 2 are wired separately, and the system bus input/output circuit 3
Since the power supply terminal and ground terminal of the system bus input/output circuit 3 and the power supply terminal and ground terminal of the internal circuit 2 are provided separately, noise generated from the system bus input/output circuit 3 does not affect the internal circuit 2.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a one-chip microcomputer according to an embodiment of the present invention. In Figure 1,
Components corresponding to those shown in FIG. 2 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 1, reference numeral 10 indicates power supply metal wiring connecting the internal circuit 2 and the power supply terminal 5, 11 indicates the power supply metal interconnection connecting the system bus input/output circuit 3 and the power supply terminal 6, and 12 indicates the internal circuit 2 and the ground terminal 8. A ground metal wiring 13 connects the system bus input/output circuit 3 and the ground terminal 9. In this embodiment, the power supply metal wiring 10 and the power supply metal wiring 11 are wired separately, and the ground metal wiring 12 and the ground metal wiring 13 are wired separately. The power supply terminal 6 and ground terminal 9 of the system bus input/output circuit 3 may be wired close to each other. In addition, terminals 5, 6,
8 and 9 may also be wired close to each other.

Next, the operation of this embodiment will be explained. For example, even if the operation of the system bus input/output circuit 3 changes greatly due to a single signal change and noise is applied to the power supply or ground, the power supply metal wiring 10 and the power supply metal The wiring 11 is wired separately, and the ground metal wiring 12 and the ground metal wiring 13 are wired separately, so the system bus input/output circuit 3
It is possible to prevent the internal circuit 2 from being affected by the noise generated in the above.

Note that when the semiconductor substrate in the chip 1 of the one-chip microcomputer is at the same potential as the power supply or ground, the power supply system of the system bus input/output circuit 3 and the power supply system of the internal circuit 2 are connected through the semiconductor substrate. However, since the impedance of the semiconductor substrate is much higher than that of metal wiring, the noise is attenuated and has almost no effect on the internal circuit 2.

[0011]

As described above, according to the present invention, the power supply wiring and ground wiring of the system bus input/output circuit and the power supply wiring and ground wiring of the internal circuit are wired separately, and the power supply terminal of the system bus input/output circuit is connected separately. Since the power supply terminal and ground terminal of the internal circuit and the ground terminal are provided separately, transmission of noise generated in the system bus input/output circuit to the internal circuit can be suppressed as much as possible, and malfunction can be prevented. The effect is that a highly reliable one-chip microcomputer can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a one-chip microcomputer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional one-chip microcomputer.

[Explanation of symbols]

2 Internal circuit 3 System bus input/output circuit 5, 6 Power terminal 8, 9 Ground terminal

Claims (1)

[Claims] Claim 1: In a one-chip microcomputer comprising a system bus input/output circuit for inputting and outputting data and an internal circuit provided in addition to the system bus input/output circuit, power supply wiring for the system bus input/output circuit. The ground wiring and the power wiring and ground wiring of the internal circuit are wired separately, and the power terminal and ground terminal of the system bus input/output circuit and the power terminal and ground terminal of the internal circuit are provided separately. A one-chip microcomputer characterized by: