JP2004297637A - Multifunctional pin control apparatus and semiconductor integrated circuit device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide techniques for controlling a multifunctional pin for assigning a plurality of functions to a single pin so as to prevent the malfunction or damage of a semiconductor integrated circuit device or an external circuit when positive logic and negative logic coexist or an input and an output coexist in the multifunctional pin. <P>SOLUTION: A switching circuit 11 is provided for switching a signal line TXD that connects a multifunctional pin 14 of a semiconductor integrated circuit device 12 and an external circuit 13 into either an unconnected state or a connected state. The switching circuit 11 then turns the signal line TXD into the unconnected state in an initial state and turns the signal line TXD into the connected state after the external circuit 13 corresponding to a function selected for the multifunctional pin 14 is connected to the signal line TXD. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multi-function pin control device or a semiconductor integrated circuit device, and more particularly to a technology effective when applied to a multi-function pin control technology for assigning a plurality of functions to the same pin.
[0002]
[Prior art]
As a technique studied by the inventor of the present invention, a technique described in Patent Literature 1 is cited as an example of a technique for controlling a multi-function pin.
[0003]
The technique disclosed in Patent Document 1 selects one of two devices connected to one communication port of a serial communication device built in a semiconductor integrated circuit device (hereinafter, referred to as “LSI (Large Scale Integrated Circuit)”). When serial communication is performed, the pull-up / pull-down control device connected to the transmission signal line switches the pull-up / pull-down before turning on the power, and sets the transmission signal line to “low” or “high”. This is for selecting a device to communicate with.
[0004]
[Patent Document 1]
JP 2001-97094 A (page 3)
[0005]
[Problems to be solved by the invention]
By the way, as a result of the present inventor's study on the multi-function pin control technique as described above, the following has been clarified.
[0006]
For example, the technique disclosed in Patent Document 1 selects a device to communicate by setting a transmission signal line to “low” or “high”, and the initial value of the transmission signal line is “low” or “high”. There is a problem that depending on the type of the connected device, a malfunction may occur due to the setting of the transmission signal line.
[0007]
In other words, no consideration is given to controlling according to the operating conditions of the device to be connected, such as whether to operate at “low” or “high”. Therefore, there is a problem that a connected device is damaged depending on an incorrect setting.
[0008]
Therefore, an object of the present invention is to provide a technique capable of preventing a malfunction or damage of an LSI or an external circuit in a multi-function pin in which a plurality of functions are assigned to the same pin.
[0009]
The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.
[0010]
[Means for Solving the Problems]
The following is a brief description of an outline of typical inventions disclosed in the present application.
[0011]
(1) A multi-function pin control device according to the present invention includes a switching circuit that switches a signal line connecting a multi-function pin of a semiconductor integrated circuit device to an external circuit to either an unconnected state or a connected state. In the initial state, the signal line is not connected, and after the external circuit corresponding to the function selected for the multi-function pin is connected to the signal line, the signal line is connected.
[0012]
(2) A multi-function pin control device according to the present invention, wherein the switching circuit is provided inside a semiconductor integrated circuit device, and a signal line connecting an internal circuit and a multi-function pin is switched between an unconnected state and a connected state. is there.
[0013]
(3) In the multi-function pin control device according to (1) or (2), the multi-function pin has a mixture of positive logic and negative logic.
[0014]
(4) In the multi-function pin control device of (1) to (3), the multi-function pin has an input function and an output function mixed.
[0015]
(5) A semiconductor integrated circuit device according to the present invention includes the multi-function pin control device of (1) to (4).
[0016]
Therefore, according to the above (1) to (5), by providing the switching circuit, malfunction of the system using the LSI having the multi-function pin is prevented, and destruction of the LSI and the external circuit connected to the LSI is prevented. Is prevented. Also, functions having different signal meanings can be assigned to the same pin, and the number of pins of the LSI can be reduced.
[0017]
According to the above (2) to (5), since the switching circuit is built in the LSI, an external circuit is not required and the number of components of the system is reduced.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for describing the embodiments, the same members are denoted by the same reference numerals, and a repeated description thereof will be omitted.
[0019]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of the multi-function pin control device according to the first embodiment of the present invention.
[0020]
First, an example of the configuration of the multi-function pin control device according to the first embodiment will be described with reference to FIG. The multi-function pin control device according to the first embodiment includes, for example, a switching circuit 11, and the switching circuit 11 is connected between a transmission signal line TXD connecting the multi-function pin 14 of the LSI 12 and the external circuit 13. ing.
[0021]
The switching circuit 11 is a circuit that can electrically or physically switch the transmission signal line TXD connecting the multi-function pin 14 of the LSI 12 and the external circuit 13 to either an unconnected state or a connected state. It is controlled by an external CPU (not shown) or the like. Further, the switching circuit 11 is configured by, for example, a tri-state buffer.
[0022]
The LSI 12 is, for example, a system LSI for a car navigation system, and includes a CPU, a memory, a register, a serial data communication circuit (SCIF: Serial Communication Interface), an infrared data communication circuit (IrDA: Infrared Data Association), and the like. Further, the control pin for serial data communication and the control pin for infrared data communication have one transmission and one reception pin, and are assigned to the same pin because they have similar functions and the same number of pins. That is, the multi-function pin 14 of the LSI 12 is a pin that also serves as the signal line TXD for transmitting serial data communication and infrared data communication. The signal line RXD is a signal line for receiving serial data communication and infrared data communication.
[0023]
The external circuit 13 is a module that performs, for example, serial data communication or infrared data communication, and is connected to devices such as a GPS (Global Positioning System), an ETC (Electronic Toll Collection), an FM tuner, and a wireless modem.
[0024]
Next, the operation of the multi-function pin control device according to the first embodiment will be described. As described above, since the multi-function pin 14 of the LSI 12 has a pin configuration that also serves as the signal line TXD for transmission of serial data communication and infrared data communication, the setting is switched according to the function to be used. Switching between serial data communication and infrared data communication is performed by a register built in the LSI 12. When the register is set to be used for infrared data communication, the transmission signal on the signal line TXD switches to positive logic (high active) in accordance with the polarity of the transmission signal of the infrared data communication module.
[0025]
However, since serial data communication is selected as the initial state of the multi-function pin 14, if the infrared data communication module is connected to the multi-function pin 14 as the external circuit 13, the pin connection and the external circuit match. Not a problem.
[0026]
In the serial data communication of the initial value, the transmission signal of the signal line TXD is negative logic (low active), so that the initial signal is “high”, and when the signal line TXD is connected, the infrared signal of the external circuit 13 is output. The data communication module becomes active. This state is maintained until a register built in the LSI 12 is set to be used for infrared data communication. Therefore, there is a risk that the infrared data communication module of the external circuit 13 will be destroyed.
[0027]
Thus, the switching circuit 11 sets the transmission signal line TXD to the unconnected state in the initial state, and switches the function of the multi-function pin 14 to infrared data communication, and then sets the signal line TXD to the connected state. Thereby, malfunction or destruction of the external circuit 13 can be prevented.
[0028]
That is, in the initial state, the multi-function pin 14 of the LSI 12 and the external circuit 13 are not connected. The function of the pin to be used is selected, and if the external circuit 13 corresponding to the selected function is connected, the signal line TXD connecting the multi-function pin 14 and the external circuit 13 is connected. This allows the system to operate normally.
[0029]
Further, even when the external circuit 13 and the pin function not corresponding thereto are selected, the signal line TXD is disconnected unless the connection state is established, so that the LSI 12 and the external circuit 13 are not adversely affected. Malfunction and destruction of the LSI 12 and the external circuit 13 can be prevented.
[0030]
(Embodiment 2)
FIG. 2 is a block diagram showing a configuration of the multi-function pin control device according to the second embodiment of the present invention.
[0031]
The multifunction pin control device according to the second embodiment has the switching circuit of the first embodiment built in an LSI. That is, the switching circuit 21 is provided between the internal circuit of the LSI 22 and the multi-function pin 24, the signal line connecting the multi-function pin 24 and the TXD pin of the external circuit 13 is separated inside the LSI 22, and the internal circuit of the LSI 22 is connected to the external circuit. The circuit 13 controls disconnection and connection with a signal line connecting the TXD pin. The control of the switching circuit 21 is performed by an internal or external CPU of the LSI 22 in the same manner as in the first embodiment.
[0032]
With the above configuration, after switching the pin function to infrared data communication, a register built in the LSI 22 is set, and a signal line connecting the external circuit 13 and the internal circuit of the LSI 22 is connected. As a result, while having the effects of the first embodiment, an external circuit is not required, and the number of components in the entire system is reduced.
[0033]
As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist thereof. Needless to say.
[0034]
For example, in the above-described embodiment, the signal line TXD for transmission of serial data communication and infrared data communication has been described as a multi-function pin. However, the present invention is not limited to this, and is widely applied to the signal line RXD of reception. This is possible, and is particularly effective for a pin in which positive logic and negative logic are mixed.
[0035]
Further, the present invention can be applied to pins other than the serial data communication and the infrared data communication. For example, the present invention can be widely applied to a pin having both an input function and an output function.
[0036]
Further, in the above-described embodiment, a system LSI for a car navigation system has been described. However, the present invention is not limited to this, and can be widely applied to other system LSIs.
[0037]
【The invention's effect】
The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.
[0038]
(1) Malfunction of a system using an LSI having multi-function pins is prevented.
[0039]
(2) Destruction of an LSI having a multifunctional pin is prevented.
[0040]
(3) Destruction of an external circuit connected to an LSI having a multi-function pin is prevented.
[0041]
(4) A multi-function pin configuration in which functions having different meanings of signals (reverse phase, input / output, etc.) are assigned to the same pin becomes possible, and the number of pins of the LSI is reduced.
[0042]
(5) Since the switching circuit is built in the LSI, no external circuit is required, and the number of components in the system is reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a multi-function pin control device according to a first embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a multi-function pin control device according to a second embodiment of the present invention.
[Explanation of symbols]
11,21 switching circuits 12,22 semiconductor integrated circuit device (LSI)
13 External circuit 14, 24 Multi-function pin TXD, RXD signal line

Claims (5)

A switching circuit for switching a signal line connecting the multifunction pin of the semiconductor integrated circuit device and the external circuit to either an unconnected state or a connected state,
The switching circuit sets the signal line to an unconnected state in an initial state, and sets the signal line to a connected state after an external circuit corresponding to a function selected for the multi-function pin is connected to the signal line. Characteristic multi-function pin control device. A switching circuit for switching a signal line connecting the internal circuit of the semiconductor integrated circuit device and the multifunction pin to either an unconnected state or a connected state,
The switching circuit sets the signal line to an unconnected state in an initial state, and sets the signal line to a connected state after an external circuit corresponding to a function selected for the multi-function pin is connected to the multi-function pin. A multifunctional pin control device characterized by the following. The multi-function pin control device according to claim 1 or 2,
A multi-function pin control device, wherein the multi-function pin has a mixture of positive logic and negative logic. The multi-function pin control device according to any one of claims 1 to 3,
The multi-function pin control device according to claim 1, wherein the multi-function pin has both an input function and an output function. A semiconductor integrated circuit device comprising the multi-function pin control device according to claim 1.

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