JP2017146757A - Signal input/output system between microcomputer and external device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal input/output system between a microcomputer and an external device capable of inputting/outputting a signal between one terminal of the microcomputer and two terminals of the external device.SOLUTION: There are provided: a microcomputer 100 having an input/output terminal A selectively set to either an output port or an input port; a processor 200 having a reset terminal R as the input port and an output terminal O as the output port; and a signal conversion circuit 300 connected between the microcomputer 100 and the processor 200, therein the signal conversion circuit 300 inputs a signal which is turned to a low level when the input/output terminal A of the microcomputer 100 is used as the output port, and which is turned to a high level when the input/output terminal A is used as the input port to the reset terminal R of the processor 200.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a signal input / output system between a microcomputer and an external device that inputs and outputs signals between a terminal of the microcomputer and a terminal of the external device.

  Conventionally, a configuration is known in which a switch input line and output signal line of a load are shared by a single port of a microcomputer, so that the switch status reading and load driving are performed by a common input / output port. (For example, refer to Patent Document 1). In this configuration, the microcomputer reads the high / low state of the signal corresponding to the on / off operation of the switch through the input / output port, and the microcomputer is connected to the same input / output port with the switch turned on. The load can be driven by turning on the transistor.

JP 2000-319969 A

  Incidentally, in the configuration disclosed in Patent Document 1 described above, since it is necessary to turn on a switch when outputting a signal for driving a load, one input / output port of a microcomputer, an input port of an external device, and It could not be used in the form of connecting to the output port. For example, a signal having a high / low state corresponding to the on / off operation of the switch can be input from the output port of the external device to the input / output port of the microcomputer to monitor the high / low state. Without operation, a signal cannot be output from the input / output port of the microcomputer and input to the input port of the external device.

  The present invention was created in view of the above points, and an object thereof is a microcomputer capable of inputting and outputting signals between one terminal of the microcomputer and two terminals of an external device. It is to provide a signal input / output system between the external device and the external device.

  In order to solve the above-described problem, a signal input / output system between the microcomputer of the present invention and an external device includes a microcomputer having a first terminal selectively set to either an output port or an input port. A signal between a microcomputer and an external device, comprising: an external device having a second terminal serving as an input port and a third terminal serving as an output port; and a signal conversion circuit connected between the microcomputer and the external device In the input / output system, the signal conversion circuit is in a high or low state when the first terminal is used as an output port, and is either the high or low state when the first terminal is used as an input port. A signal in the state is input to the second terminal.

  Since the signal to be input to the external device is generated using the case where the terminal of the microcomputer is used as the input port, the signal output from the terminal as the output port of the external device is generated using one terminal of the microcomputer. The reading operation and the operation of inputting a signal to the terminal as the input port of the external device can be performed in parallel. Thereby, the number of terminals of the microcomputer can be reduced.

  In addition, it is desirable that the above-described external device perform an operation of outputting a signal from the third terminal toward the microcomputer when one of the high and low signals is input to the second terminal. . As a result, signal input / output operations with respect to the two terminals of the external device can be simultaneously enabled.

  Further, the microcomputer described above maintains the first terminal in a high impedance state when used as an input port, and the signal conversion circuit is connected to the second terminal when the first terminal is in a high impedance state. It is desirable to input a signal that is in the other state of low. As a result, the microcomputer can simultaneously perform the signal input operation and the output operation via one terminal.

  Further, when the above-described microcomputer uses the first terminal as the input port, it is desirable to detect the voltage of the signal applied to the first terminal. Conventionally, a microcomputer having the functions of an output port and an analog input port in a single terminal is generally used. Such a terminal is applied to the present invention, and this terminal is connected to two terminals of an external device. It becomes possible to do.

  Further, it is desirable that the first terminal described above is an input / output terminal of the microcomputer, the second terminal is a reset terminal of the processor, and the third terminal is an output terminal of the processor. Thus, signals can be input / output between the two terminals of the processor using the input / output terminals of the microcomputer.

It is a figure which shows the structure of the electronic device of one Embodiment. It is a figure which shows the content of the signal input / output via the signal conversion circuit shown in FIG. It is a figure which shows the other example of an external device. It is a figure which shows the other example of an external device. It is a figure which shows the other example of an external device. It is a figure which shows the other example of an external device. It is a figure which shows the modification at the time of using a low active processor.

  Hereinafter, an electronic apparatus according to an embodiment to which the present invention is applied will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of an electronic apparatus according to an embodiment. As shown in FIG. 1, the electronic apparatus of this embodiment includes a microcomputer 100, a processor 200, and a signal conversion circuit 300.

  The microcomputer 100 operates in synchronization with the operation clock signal, and performs various operations by executing predetermined programs. The microcomputer 100 includes an input / output terminal A that receives a watchdog signal output from the processor 200 and outputs a reset signal that initializes the operation toward the processor 200. The input / output terminal A receives a watchdog signal output from the processor 200 when used as an analog input port. Further, when this input / output terminal A is used as an output port, a reset signal is output to the processor 200. In this embodiment, the processor 200 is a monitoring target by the microcomputer 100.

  For example, the processor 200 performs a signal processing operation after being initialized when a reset signal output from the microcomputer 100 is input, and inputs a watchdog signal to the microcomputer 100 when a predetermined exceptional operation occurs. Output to output terminal A. The processor 200 includes a reset terminal R to which a reset signal is input and an output terminal O that outputs a watchdog signal toward an input / output terminal A of the microcomputer 100.

  The signal conversion circuit 300 is connected (inserted) between the microcomputer 100 and the processor 200 as an external device, and inputs and outputs a reset signal and a watchdog signal between the microcomputer 100 and the processor 200.

  A specific example of the signal conversion circuit 300 is shown in FIG. For example, as illustrated in FIG. 1, the signal conversion circuit 300 includes two transistors Tr1 and Tr2 and five resistors R1 to R5.

  One end of each of resistors R1, R2, and R5 is connected to the input / output terminal A of the microcomputer 100. The other end of the resistor R1 is connected to a power supply line of 3.3 V, for example, together with the emitter of the transistor Tr2. The other end of the resistor R2 is connected to the base of the transistor Tr1. The collector of the transistor Tr1 is connected to the base of the transistor Tr2 via the resistor R3. The collector of the transistor Tr2 is connected to the reset terminal R of the processor 200 together with one end of the resistor R4. The emitter of the transistor Tr1 is grounded together with the other end of the resistor R4. The other end of the resistor R5 is connected to the output terminal O of the processor 200.

  FIG. 2 is a diagram showing the contents of signals input / output via the signal conversion circuit 300 shown in FIG. Specifically, in the signal conversion circuit 300, when the low level signal is input from the input / output terminal A as the output port of the microcomputer 100, the two transistors Tr1 and Tr2 are both turned off. A low level signal (reset signal) is input to the reset terminal R. As a result, the processor 200 is reset.

  Further, since the two transistors Tr1 and Tr2 are both turned on when the input / output terminal A as the analog input port of the microcomputer 100 is in a high impedance state, the signal conversion circuit 300 is connected to the reset terminal R of the processor 200. Input level signal. This enables the operation of the processor 200.

  In parallel with this operation, a signal output from the output terminal O of the processor 200 is input to the input / output terminal A of the microcomputer 100. The microcomputer 100 determines the high / low state of this signal based on the voltage value applied to the input / output terminal A.

  For example, if the resistor R1 is 10 kΩ, the resistor R2 is 47 kΩ, and the resistor R5 is 22 kΩ, a voltage of about 2.1 V is applied to the input / output terminal A of the microcomputer 100 when the output terminal of the processor 200 is low level. At the level, a voltage of about 2.8 V is applied to the input / output terminal A of the microcomputer 100. Accordingly, in the microcomputer 100, the high / low state of the signal output from the output terminal O of the processor 200 is set by setting the threshold value to about 2.5 V and comparing it with the voltage applied to the input / output terminal A. Can be determined. Further, the signal input to the input / output terminal A of the microcomputer 100 can determine that the processor 200 is in a predetermined exceptional operation when in the low state. At this time, the microcomputer 100 causes the processor 200 to recover. The process is implemented.

  As described above, in the electronic apparatus according to the present embodiment, the case where the input / output terminal A (first terminal) of the microcomputer 100 is used as an input port (in a high impedance state) is used. Since the signal to be input to the reset terminal R is generated, an operation of reading a signal output from the output terminal O as an output port of the processor 200 using one input / output terminal A of the microcomputer 100, The operation of inputting a signal to the reset terminal R as an input port can be performed in parallel. Thereby, the number of terminals of the microcomputer 100 can be reduced.

  Further, the processor 200 operates to output a signal from the output terminal O (third terminal) to the microcomputer 100 during a period in which a high-level signal is input to the reset terminal R (second terminal). Is going. As a result, signal input / output operations for the two terminals of the processor 200 can be simultaneously enabled.

  Specifically, when the microcomputer 100 is used as an input port, the input / output terminal A is maintained in a high impedance state, and the signal conversion circuit 300 is connected to the processor 200 when the input / output terminal A is in a high impedance state. A high level signal is input to the reset terminal R. As a result, the microcomputer 100 can simultaneously perform the signal input operation and the output operation via the single input / output terminal A.

  The microcomputer 100 detects the voltage of the signal applied to the input / output terminal A by using the input / output terminal A as an analog input port. Conventionally, a microcomputer in which functions of an output port and an analog input port are provided in one terminal is generally used. Such a terminal is applied to the present invention, and the input / output terminal A as this terminal is set as the processor 200. It is possible to connect to these two terminals.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. For example, in the above-described embodiment, the processor 200 has been described as an example of the external device. However, the present invention can be applied to the case where other external devices are used.

  3 to 6 are diagrams illustrating other examples of the external device. In the example shown in FIG. 3, a high side switch (high side SW) 200A as an external device is used. The high-side switch 200A is for blocking / conducting inserted in the power supply line, and has an enable terminal EN (second terminal) and an overcurrent terminal OC (third terminal). When a high level signal is input to the enable terminal EN, the operation of the high side switch 200A becomes valid. Further, when an overcurrent of the power supply line is detected, a high level signal is output from the overcurrent terminal OC, and a low level signal is output in other cases.

  In the example shown in FIG. 4, a DCDC converter (DC / DC) 200B as an external device is used. The DCDC converter 200B has an enable terminal EN (second terminal) and a power good terminal PG (third terminal). When a high level signal is input to the enable terminal EN, the operation of the DCDC converter 200B is enabled. When the voltage supply is in a predetermined stable state, a high level signal is output from the power good terminal PG, and at other times, a low level signal is output.

  In the example shown in FIG. 5, a DSP (digital signal processor) 200C as an external device is used. The DSP 200C has a reset terminal R (second terminal) and an enable EN (third terminal). When a low level signal is input to the reset terminal R, the operation of the DSP 200C is reset. When the operation is enabled, a high level signal is output from the enable terminal EN, and a low level signal is output otherwise.

  In the example shown in FIG. 6, a CD mechanism IC (CD Mech) 200D as an external device is used. This CD mechanism IC 200D is for controlling the mechanism part of the CD drive unit, and has a standby terminal SB (second terminal) and a zero mute terminal ZM (third terminal). The operation of the CD mechanism IC 200D becomes effective when a high level signal is input to the standby terminal SB. Further, when the signal level output from the CD drive unit is 0, a high level signal is output from the zero mute terminal ZM, and otherwise, a low level signal is output.

  In the above-described embodiment, the reset operation is performed when a low-level signal is input to the reset terminal R of the processor 200, and the operation is enabled when a high-level signal is input. However, on the contrary, the reset operation is performed when a high level signal is input to the reset terminal R, and the operation becomes valid when a low level signal is input. In some cases, the present invention can be applied.

  FIG. 7 is a diagram illustrating a modification in the case where the low-active processor 200 ′ is used. The signal conversion circuit 300A shown in FIG. 7 differs from the signal conversion circuit 300 shown in FIG. 1 in that the transistor Tr2 and the resistors R4 and R4 are replaced with a resistor R6. In this signal conversion circuit 300A, when a high level signal is input from the input / output terminal A as an output port of the microcomputer 100, the transistor Tr1 is turned off. (Reset signal) is input. As a result, the processor 200 is reset.

  The signal conversion circuit 300A inputs a low level signal to the reset terminal R of the processor 200 because the transistor Tr1 is turned on when the input / output terminal A as an analog input port of the microcomputer 100 is in a high impedance state. To do. This enables the operation of the processor 200.

  As described above, according to the present invention, since the signal input to the external device is generated using the case where the terminal of the microcomputer is used as the input port, the one of the terminal of the microcomputer is used to generate the signal of the external device. An operation of reading a signal output from a terminal as an output port and an operation of inputting a signal to a terminal as an input port of an external device can be performed in parallel. Thereby, the number of terminals of the microcomputer can be reduced.

100 microcomputer 200 processor 200A high side switch 200B DCDC converter 200C DSP
200D CD mechanism IC
300, 300A signal conversion circuit

Claims (5)

A microcomputer having a first terminal selectively set to either an output port or an input port; an external device having a second terminal serving as an input port; and a third terminal serving as an output port; In a signal input / output system between a microcomputer and an external device, comprising a signal conversion circuit connected between the computer and the external device,
The signal conversion circuit is in a high or low state when the first terminal is used as an output port, and is in a high or low state when the first terminal is used as an input port. A signal input / output system between a microcomputer and an external device, wherein the signal is input to the second terminal. In claim 1,
The external device performs an operation of outputting a signal from the third terminal toward the microcomputer when one of a high signal and a low signal is input to the second terminal. Signal input / output method between the microcomputer and external devices. In claim 1 or 2,
The microcomputer maintains the first terminal in a high impedance state when used as an input port;
A microcomputer and an external device, wherein the signal conversion circuit inputs a signal that is in either the high state or the low state to the second terminal when the first terminal is in a high impedance state. Signal input / output system between. In any one of Claims 1-3,
When the microcomputer uses the first terminal as an input port, the microcomputer detects a voltage of a signal applied to the first terminal, and a signal input / output system between the microcomputer and an external device . In any one of Claims 1-4,
The first terminal is an input / output terminal of the microcomputer;
The second terminal is a reset terminal of the processor;
A signal input / output system between a microcomputer and an external device, wherein the third terminal is an output terminal of the processor.

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