JP2760691B2 - Electronic circuit having mode-changeable internal circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit such as a semiconductor circuit, and more particularly to an electronic circuit having a mode-changeable internal circuit which requires testing and adjustment of the internal circuit.

[0002]

2. Description of the Related Art FIG. 5 is a schematic diagram showing an example of a system configuration in a semiconductor circuit among conventional electronic circuits. In FIG. 5, 1 is an output terminal, 2 is a timer A, 3 is a timer B, and 4 is a timer C. Reference numeral 5 denotes a dedicated timer, which is controlled by a control circuit (not shown). 6 is an inverter, 7 is a capacitor, 8 is a variable capacitor, 9 and 10 are GND (earth), and 11 is an oscillator. Reference numeral 12 denotes a timepiece. This timepiece 12 has an inverter 6, a capacitor 7, a variable capacitor 8, a GND 9,
10 and an oscillator 11. Reference numeral 63 denotes a functional circuit. The functional circuit 63 includes a clock 12 and a timer A2.
And a timer B3 and a timer C4. 64
Is a semiconductor circuit, and the semiconductor circuit 64 includes an output terminal 1, a timer A2, a timer B3, a timer C4, and a dedicated timer 5. Reference numeral 15 denotes a measuring device for testing and adjusting the internal circuit.

The variable capacitor 8 has one end connected to the GND 10 and the other end connected to one end of the oscillator 11 and the input side of the inverter 6. Capacitor 7 is connected to one end GND9, the other ends of the oscillator 11, the output side of the inverter 6, the input side of the timer A2, the input side of the timer B3, further
It is connected to the input side of the dedicated timer 5. Timer C4
The input side is connected to an external input terminal or register.
You. The output side of the timer A2, the output side of the timer B3, and the output side of the timer C4 are each connected to a circuit (not shown) in the semiconductor circuit 64, and the other end of the dedicated timer 5 is connected to the measuring device 15 via the output terminal 1. Is connected to

In the normal operation of the semiconductor circuit 14 shown in FIG. 5, the measuring device 15 is not connected, and the timers A2, B3 and C4 are connected to the respective circuits (not shown) of the semiconductor circuit 64 respectively. A signal having a predetermined frequency is output.

Next, a description will be given of a case where a test or adjustment of the semiconductor circuit 64 is performed, for example, a case where a reference frequency of the timepiece 12 is adjusted. When adjusting the reference frequency of the timepiece 12, for example, a measuring instrument 15 such as an oscilloscope is connected to the output terminal 1. The signal of the frequency of the clock 12 is frequency-divided by the dedicated timer 5 and converted into a frequency that can be easily observed by a measuring device 15 such as an oscilloscope. The inspector adjusts the reference frequency of the timepiece 12 by adjusting the capacity of the variable capacitor 8 while observing the output signal of the dedicated timer 5 with the measuring device 15.

FIG. 5 shows a case where a dedicated timer is provided for testing, adjustment, etc.
Further, as shown in FIG. 6, a logic circuit may be provided in the timer A2, the timer B3, and the timer C4 included in the functional circuit 13 in place of the dedicated timer 5. That is,
FIG. 6 is a schematic diagram showing another example of a system configuration in a conventional semiconductor circuit, wherein 1 to 4, 6 to 12, and 15 have the same functions as those in FIG. 16-18 are OR gates, 19-24 are AND gates, 25-28
Is an inverter, 29 is GND, and 30 is an input terminal.
Reference numeral 13 denotes a functional circuit different from the circuit configuration of FIG. 5, and the functional circuit 13 includes a clock 12, a timer A2, a timer B3, a timer C4, OR (OR) gates 16 to 18, AND gates 19 to 24, and an inverter 25. To 27 and GND 29. Reference numeral 14 denotes a semiconductor circuit different from the circuit configuration shown in FIG. 5, and the semiconductor circuit 14 includes an output terminal 1, an input terminal 30, a functional circuit 13, and an inverter 28.

The variable capacitor 8 has one end connected to the GND 10 and the other end connected to one end of the oscillator 11 and the input side of the inverter 6. One end of the capacitor 7 is connected to the GND 9, and the other end is connected to the other end of the oscillator 11, the output side of the inverter 6, the input side of the timer A 2, and one input side of the AND gate 20. The output side of the timer A2 is connected to a circuit (not shown) in the semiconductor circuit 14 and one input side of the AND gate 19. The OR gate 16 has one input side connected to the output side of the AND gate 19, the other input side connected to the output side of the AND gate 20, and the output side connected to the input side of the timer B3. The output of the timer B3 is a circuit (not shown) in the semiconductor circuit 14 and the AND gate 2
1 is connected to one input side. The AND gate 22 has one input side connected to an external input terminal or a register (not shown). The OR gate 17 has one input side connected to the output side of the AND gate 21, the other input side connected to the output side of the AND gate 22, and the output side connected to the input side of the timer C4. The output side of the timer C4 is connected to a circuit (not shown) in the semiconductor circuit 14 and one input side of the AND gate 23. The AND gate 24 has one input side connected to the GND 29. The OR gate 18 has one input side as an AND gate 23.
Is connected to the output side of the AND gate 24, and the output side is connected to the measuring instrument 15 via the output terminal 1. The inverter 28 has an input terminal 3
0 and the output side is AND gates 19, 20, 23
, The other input of the AND gate 20 via the inverter 25, the other input of the AND gate 22 via the inverter 26, and the
It is connected to the other input side of the D gate 24.

In the normal operation of the semiconductor circuit 14 shown in FIG. 6, the measuring device 15 is not connected. Here, when the "H" signal is input to the input terminal 30, the output of the inverter 28 is inverted to be in the state of the "L" signal. As a result, the AND gates 19, 21 and 23 are invalid, and
Gates 20, 22, 24 are inverters 25, 26, 27
Becomes valid with the “H” signal. Timer A2, Timer B
Reference numeral 3 denotes a semiconductor circuit based on the output signal of the clock 12.
4 outputs a signal of a predetermined frequency required for a circuit (not shown). Further, the timer C4 outputs a signal of a predetermined frequency required for a circuit (not shown) of the semiconductor circuit 14 based on a signal from an external input terminal or a register.

Next, a description will be given of a case where a test or adjustment is performed in the semiconductor circuit of FIG. 6, that is, a case where a reference frequency similar to that of FIG. 5 is adjusted. First, a measuring instrument 15 such as an oscilloscope is connected to the input terminal 1, and an “L” signal is input to the input terminal 30. The inverter 28 inverts the "L" signal from the input terminal 30,
An "H" signal is output. As a result, the AND gate 19,
21 and 23 are valid, the AND gates 20, 22, and 24 are invalid, and the clock 1 is used instead of the dedicated timer 5 in FIG.
The timer A2, the timer B3, and the timer C4 are connected in series between the timer 2 and the measuring device 15, and the signal of the output frequency of the clock 12 is divided into a frequency that can be easily observed by the measuring device 15. Then, the inspector observes the output signals of the timers A2, B3, and C4 with the measuring instrument 15 via the AND gate 23, the OR gate 18, and the output terminal 1,
The timepiece 12 is adjusted by adjusting the capacity of the variable capacitor 8.

A mode switching register 40 may be used instead of the input terminal 30 in FIG. That is, as shown in FIG. 7, for example, a mode switching register 40 is built in the semiconductor circuit 14, and the output of the register is connected to the input of the inverter 28. During normal operation, “1” is written in the mode switching register 40 so that the “H” signal is input to the inverter 28. As a result, similarly to the case of the normal operation in FIG. 6, a signal of a predetermined frequency required for a circuit (not shown) of the semiconductor circuit 41 can be output from the timer A2, the timer B3, and the timer C4. Also,
At the time of test or adjustment, "0" is externally written to the mode switching register 40, and the "L" signal is input to the inverter 28, which is similar to the case where the "L" signal is input to the input terminal 30 in FIG. Let the action take place.

[0011]

In a conventional electronic circuit,
When performing a test or adjustment, it is necessary to provide a dedicated hardware such as a dedicated timer for a test or the like, a dedicated input terminal, and a mode switching register for switching a mode.
For this reason, there is a problem that the dedicated hardware becomes relatively large. Further, there is a problem that it is generally not preferable to increase the number of input terminals in the semiconductor circuit, and there is a problem that adjustment with another circuit function is required when a mode switching register is provided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems that occur when testing or adjusting an electronic circuit, and it is unnecessary to increase the number of dedicated hardware and input terminals and to add a mode switching register. It is an object of the present invention to provide an electronic circuit having a mode-changeable internal circuit.

[0013]

As shown in FIG. 1, the electronic circuit according to the first aspect of the present invention has an internal circuit (functional circuit) which is switched to a changed function mode different from the normal operation mode based on a switching signal. 13) the power supply 32 for supplying a current to the output terminal 1 via a resistor 31 having a predetermined size, and a power supply 32 which drops to a predetermined value when an external circuit such as a measuring instrument is connected to the output terminal. And a switching circuit 35 having a switching signal output circuit (inverter 28) for detecting a voltage value to be changed and outputting a switching signal. As shown in FIG. 3, the electronic circuit according to the second invention has an electronic circuit having an internal circuit (function circuit 13a) whose function is switched to a changed function mode different from the normal operation mode in accordance with a plurality of types of switching signals. In the circuit, a power supply 32 for supplying a current to the output terminal 1 via a resistor 31 having a predetermined size
And, when the external circuit is connected to the output terminal, detects the magnitude of the voltage value of the output terminal that falls to a predetermined value depending on the magnitude of the resistance, and detects the magnitude of each voltage value. There is provided a switching circuit 35a having a plurality of switching signal output circuits (inverters 37, 36, 28) for outputting different switching signals corresponding thereto.

[0014]

In the electronic circuit according to the first invention, when the external circuit is connected to the output terminal, the voltage value of the output terminal falls to a predetermined value by a resistor. When the voltage value is detected by the switching signal output circuit, a switching signal is output to the internal circuit. Upon receiving the switching signal, the internal circuit switches to the changed function mode different from the normal mode, and outputs the signal of the internal circuit to the external circuit. Inspection personnel based on the above signals received by external circuits such as measuring instruments,
Perform tests and adjustments. When the test and adjustment are completed and the external circuit is removed from the internal circuit, the internal circuit returns to the normal function mode. The electronic circuit according to the second invention, when an external circuit such as a measuring instrument is connected,
The voltage of the output terminal decreases due to the resistance of the external circuit. This lowered voltage value is detected by a switching signal output circuit that outputs a plurality of types of switching signals. A switching signal corresponding to the lowered voltage value is output to the internal circuit to switch the internal circuit to a specific type of change function mode. The signals of the internal circuit received by the external circuit also have different magnitudes.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a schematic diagram of a semiconductor circuit according to an embodiment of the first invention. In FIG. 1, 1 is an output terminal, 2 is a timer A, 3 is a timer B, and 4 is a timer C. 6 is an inverter, 7 is a capacitor, 8 is a variable capacitor, 9.1
0 is GND (earth). Reference numeral 12 denotes a timepiece. This timepiece 12 includes an inverter 6, a capacitor 7, a variable capacitor 8, and GNDs 9 and 10. 16 ~
18 is an OR gate, 19 to 24 are AND gates, 25 to 25
27 is an inverter, and 29 is GND. Reference numeral 13 denotes a functional circuit as an internal circuit. The functional circuit 13 includes timers A2, B3, and C4, OR gates 16 to 18, AND gates 19 to 24, inverters 25 to 27, and a ground 29. 28 is an inverter as a switching signal output circuit, 31 is a resistor, 32 is a power supply, 33 is a transistor, and 34 is GND. Reference numeral 35 denotes a switching circuit. The switching circuit 35 includes an inverter 28, a resistor 31, a power supply 32, a transistor 33, and a GND 34. Reference numeral 14 denotes a semiconductor circuit. The semiconductor circuit 14 includes a functional circuit 13 and a switching circuit 35. Reference numeral 15 denotes a measuring device such as an oscilloscope for performing tests and adjustments. Since 1 to 29 have the same functions as the conventional example (FIG. 6), they are denoted by the same reference numerals as in FIG. 6, and the description of the following configuration is omitted.

The internal connection of the functional circuit 13 is the same as that of the above-described conventional example, and the description is omitted. The output terminal 1 is connected to one end of the resistor 31, the input side of the inverter 28, the transistor 3
3 is connected to one end. The other end of the resistor 31 is a power source 32
And the output side of the inverter 28 is connected to the AND gate 1
9, 21, 23, respectively, and the input sides of AND gates 20, 22, 24 and the inverters 25, 2
6 and 27 are connected. The other end of the transistor 33 is connected to the GND 34 and the gate is ORed.
It is connected to the output side of the gate 18.

FIG. 2 is a timing chart showing the operation in the embodiment of the first invention. Next, FIGS. 1 and 2
The operation of this embodiment will be described with reference to FIG. In a normal operation (operation mode), nothing is connected to the output terminal 1 and the voltage of the power supply 32 (for example, 5
V) is input, and the threshold value of the inverter 28 is 2
If it is V, since the output of the inverter 28 is an "L" signal, the AND gates 20, 22, and 24 are enabled, and the AND gates 20, 22, and 24 are disabled by the inverters 25, 26, and 27. The timers B3 and C4 output a signal of a predetermined frequency to a circuit (not shown) of the semiconductor circuit 14, respectively.

As in the prior art, when a test or adjustment is performed in the semiconductor circuit 14 (change function mode), for example, the clock 12
When the reference frequency is adjusted, a measuring instrument 15 such as an oscilloscope is connected to the output terminal 1. Then, a current supplied from the power supply 32 flows to the measuring device 15 via the resistor 31 and the output terminal 1. As a result, even if the input voltage of the inverter 28 is initially the same as the voltage of the power supply 32, for example, 5 V as in the “unconnected” period in FIG. 2, the measuring device 15 is connected to the output terminal 1. 1 by the current caused by
The voltage drops to V. For example, if the threshold value of the inverter 28 is 2 V, the output of the inverter 28 is inverted by the connection of the measuring device 15 to become an “H” signal, and a switching signal is generated. That is, the switching circuit 35 generates a switching signal to the functional circuit 13 by connecting the measuring device 15. FIG. 2 shows a change in the voltage of the output terminal 1 at this time, specifically, a change from the “unconnected” period of the timer C4 and the output terminal 1 to the “connected” period.

When the output of the inverter 28 is inverted to become an "H" signal, the AND gates 19, 21 and 23 become valid, the timers A2, B3 and C4 are connected in series, and the signal of the output frequency of the clock 12 is output. The signal is divided into signals of a frequency that can be easily observed by a measuring instrument such as an oscilloscope. Then, the output signal of the timer C4 is input to the gate of the transistor 33 of the switching circuit 35. In the transistor 33, if the input is an “L” signal, the output terminal 1 and the GND3
4 is disconnected, the voltage of the output terminal 1 becomes 1 V, and if the input of the transistor 33 is an “H” signal, the output terminal 1
And GND 34 are connected, and the voltage of the output terminal 1 becomes 0V. Therefore, timer A2, timer B3, timer C
The signal of the frequency of the clock 12 divided by 4 is observed by the measuring device 15 with an amplitude of 1V. Then, the “connection” period in FIG. 2 changes. The inspector adjusts the time of the watch 12 by adjusting the capacity of the variable capacitor 7 while observing the signal of this frequency. Incidentally, the resistance constituting the switching circuit 35 in this embodiment may be a diode or the like. Further, the switching circuit may have the function of operating the timers A2, B3 and C4 independently during normal operation, and having a function of connecting these timers in series at the time of test and adjustment, and is limited to the configuration of the above embodiment. Not something.

FIG. 3 is a schematic diagram showing an example of a system configuration of a semiconductor circuit according to an embodiment of the second invention.
In FIG. 3, reference numerals 36 and 37 denote inverters serving as switching signal output circuits, and reference numeral 35a denotes a switching circuit. This switching circuit 35a includes a resistor 31, a power supply 32, an inverter 28,
36, 37, a transistor 33 and a GND 34. 38 is a variable resistor, 40 is an oscillation circuit switcher, 50 is a frequency division selection circuit, 13a is a functional circuit as an internal circuit, and this functional circuit 13a is a clock 12
a to 12c, an oscillation circuit switching unit 40, and a frequency division selection circuit 50
It is composed of The other circuit components are the same as those in FIG. The output terminal 1 is connected to one end of a resistor 31,
Input side of inverters 37, 36, 28, transistor 3
3 is connected to one end. The other end of the resistor 32 is a power source 32
The other end of the transistor 33 is connected to the GND 34, and the gate is connected to the frequency division selection circuit 50. The output sides of the inverters 37, 36, and 28 are connected to the oscillation circuit switching unit 40 and the frequency division selection circuit 50, respectively. The clocks 12a to 12c have the same circuit configuration as that of the clock 12 in FIG. 1 described above, and the outputs of the clocks are connected to the oscillation circuit switching device 40, respectively. It is connected to the circumference selection circuit.

FIG. 4 is a timing chart showing the operation of the embodiment of FIG. Next, the operation of this embodiment will be described with reference to FIGS. In a normal operation (operation mode), a measuring instrument 15 such as an oscilloscope is not connected to the output terminal 1 or a power supply voltage (for example, 5 V) is supplied. As a result, the input voltage of the inverters 37, 36, 28
Since the voltage is 5 V, which is the same voltage value as that of the inverter 37, the inverters 37 and 3
Assuming that the threshold values of 6, 28 are 3V, 2.5V, 1.5V, the outputs of inverters 37, 36, 28 are "L".
Signal. Therefore, if the outputs of inverters 37, 36 and 28 are "L" signals, a signal of a predetermined frequency is output from the timer in the oscillator circuit switch to each circuit in semiconductor circuit 14 based on clocks 12a to 12c. .

Next, when performing a test or adjustment (change function mode), for example, when adjusting the reference oscillation frequency of the clocks 12a to 12c, a probe (measurement cable) of a measuring instrument 15 such as an oscilloscope is connected to the output terminal 1. Once connected,
The current supplied from the power supply 32 is a resistor 31, an output terminal 1,
It flows to the measuring device 15 via the variable resistor 38. Here, the variable resistor 38 of the measuring device simply means that different measuring devices 15 having different resistance values are connected. Alternatively, even if the measuring device 15 is the same, probes having different resistance values (for example, a 1: 1 probe, 1:10 probe in an oscilloscope).
Probe). Here, the probe is a measuring cable. Since the internal resistance differs depending on the different measuring instruments and probes connected to the output terminal 1, the first resistance, the second resistance, and the third resistance in FIG. 4 are obtained.

First, the measuring instrument 1 connected to the output terminal 1
5 is the “first resistance value”, the measuring device 1
When 5 is not connected, the input voltage of the inverter 37 is the same voltage as the power supply 32, for example, 5 V, as in the “unconnected” period shown in FIG. When the measuring device 15 is connected and the resistance value of the variable resistor 38 becomes the “first resistance value”, the voltage of the output terminal 1 drops to 3 V due to the current generated by the resistor 31 and the variable resistor 38. For example, if the threshold value of the inverter 37 is 4 V, the output of the inverter 37 is inverted by the connection of the measuring device 15 to become an “H” signal. Then, the first switching signal is output to the oscillation circuit switching device 40 and the frequency division selection circuit 50. As a result, the clock 12a is selected by the oscillation circuit switching unit 40, and the frequency selection circuit 50 is selected so that the signal of the output frequency of the clock 12a can be frequency-divided into a signal of a frequency observable by the measuring device 15, and the frequency division is performed. The signal of the frequency is input to the gate of the transistor 33 and output to the measuring device 15. The inspector adjusts the capacity of the variable capacitor in the clock 12 a while observing the measuring device 15. FIG. 4 shows a change in the voltage of the output terminal 1 at this time. Specifically, the voltage changes from the “unconnected” period between the functional circuit 13 and the output terminal 1 to the “connected” period of the “first resistance value”. I do.

Next, a measuring device 15 having a different resistance value is connected to the output terminal 1, and when the resistance value of the variable resistor 38 is “second resistance value”, the measuring device 15 is connected to the output terminal 1. As a result, the voltage of the output terminal 1 becomes 2
The voltage drops to V. At this time, for example, the inverter 3
If the threshold value of 6 is 2.5 V, the output of the inverters 37 and 36 is inverted by the connection of the measuring device 15 to become an “H” signal. Then, the first and second switching signals are output from the inverters 37 and 36 to the oscillation circuit switching unit 40 and the frequency division selection circuit 50. As a result, the clock is switched to the clock 12b by the oscillation circuit switch 40, and the frequency division selection circuit 5
The frequency is divided by 0 into a signal having a frequency that can be observed by the measuring device 15 and output to the measuring device 15. The inspector is a measuring instrument 1
While observing 5, the capacitance of the variable capacitor in the clock 12b is adjusted. That is, the switching circuit 35 a
The first and second switching signals are generated by the “resistance” of “connection” of the “second resistance” in the “connection” period of FIG.
Period.

Next, a measuring device 15 having a different resistance value is connected to the output terminal 1, and when the resistance value of the variable resistor 38 is “third resistance value”, the measuring device 15 is connected to the output terminal 1. As a result, the voltage at the output terminal 1 becomes 1
The voltage drops to V. At this time, for example, the inverter 28
Is 1.5V, the output of the inverters 37, 36 and 28 is inverted by the connection of the measuring instrument 15 to become an "H" signal. The first, second and third switching signals are supplied from the inverters 37, 36 and 28 to the oscillation circuit switching device 4.
0 and output to the frequency division selection circuit 50. As a result, for example, the clock is switched to the clock 12 c by the oscillation circuit switch 40, the frequency is divided into a signal having a frequency observable by the measuring device 15 by the frequency dividing selection circuit 50, and the signal is output to the measuring device 15. The inspector adjusts the capacity of the variable capacitor in the clock 13 c while observing the measuring device 15. That is, the switching circuit 35a generates the third, second, and first switching signals by the "third resistance value" of the variable resistor 38 of the measuring device 15, and outputs the "third resistance" in the "connection" period of FIG. Value ".

As described above, the inverters 37, 36, 28
Is inverted to become an "H" signal, the first, second, and third switching signals from these inverters are output to the oscillation circuit switching device 40 and the frequency division selection circuit 50. The output signal of the frequency division selection circuit 50 is input to the gate of the transistor 33 of the switching circuit 35a. If the gate of the transistor 33 is an “L” signal, the output terminal 1 and the GND 34
And the voltage at the output terminal 1 becomes 3 V, 2 V or 1 V. If the input of the transistor 33 is an “H” signal, the output terminal 1 is connected to the GND 34, and the voltage at the output terminal 1 becomes 0 V. . Therefore, the output signal of the frequency division selection circuit 50 is observed by the measuring device 15 at an amplitude of 3 V according to the first switching signal, at an amplitude of 2 V according to the second switching signal, and at an amplitude of 1 V according to the third switching signal. . Specifically, the connection period of the “first resistance value”, “second resistance value”, and “third resistance value” in the “connection” period of FIG. 4 changes.

However, depending on the operation of the functional circuit 13a,
If the gate of the transistor 33 is at the “H” signal, the output terminal 1 and the GND 34 are connected, and the voltage of the output terminal 1 becomes 0V. When the voltage at the output terminal 1 becomes 0 V, all of the inverters 37, 36, and 28 become "L" signals, and the first, second, and third switching signals are output from the oscillation circuit switching device 4.
0, output to the frequency division selection circuit 50. Therefore, all the functions of the oscillation circuit switch 40 and the frequency division selection circuit 50 by these switching signals operate. Therefore,
In order to avoid this, it is necessary to perform exclusive control so that when the function of one circuit operates, the function of the other circuit does not operate. Specifically, the latch is performed when any of the inverters 37, 36, and 28 operates, so that other circuits do not operate. As described above, the electronic circuit of the present invention does not require many conventional external terminals and the like, and can easily select an optimal circuit function.

[0028]

As described above, according to the first aspect, in an electronic circuit having an internal circuit that can be switched to a change function mode different from a normal operation mode based on a switch signal, a predetermined output terminal is provided. A power supply for supplying a current through a resistor having a magnitude, and a switching circuit having a switching signal output circuit for detecting a lowered voltage value due to connection of an external circuit such as a measuring instrument and outputting a switching signal. By providing an external circuit to the output terminal, the voltage of the internal circuit can be reduced by connecting the external circuit to the output terminal, and the function of the circuit can be switched by utilizing the voltage change. Since the state change of the circuit can be detected by the external circuit, there is no need to provide a dedicated hardware for testing, a mode switching register for switching modes, and an input terminal. Connecting road only an effect which can be tested like in. There is also an effect that the above-described effect can be realized by adding relatively small-scale hardware. According to the second aspect, in the electronic circuit having an internal circuit whose function is switched to a plurality of types of changed function modes different from the operation mode in accordance with the plurality of types of switching signals,
A power supply for supplying a current to an external circuit through a resistor, and an external circuit connected to an output terminal, and when the voltage at the output terminal drops, a plurality of switching signals that output different switching signals according to the magnitude of the drop to the internal circuit. Since the switching signal output circuit and the switching circuit are provided in the switching circuit, there is an effect that a plurality of switching functions can be provided in addition to the effect of the first invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a system configuration of a semiconductor circuit according to an embodiment of the first invention.

FIG. 2 is a timing chart showing the operation of FIG.

FIG. 3 is a schematic diagram showing a system configuration of a semiconductor circuit according to one embodiment of the second invention.

FIG. 4 is a timing chart showing the operation of FIG. 3;

FIG. 5 is a schematic diagram showing a configuration of a semiconductor circuit showing an example of a conventional technique.

FIG. 6 is a schematic diagram similar to FIG. 5;

FIG. 7 is a schematic diagram showing a configuration of a semiconductor circuit showing another example of the related art.

[Explanation of symbols]

 Reference Signs List 1 output terminal 13, 13a functional circuit 28, 36, 37 inverter 31 resistor 32 power supply 33 transistor 35, 35a switching circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 27/04 G01R 31/319 H01L 21/66 H01L 21/822

Claims (2)

(57) [Claims] An internal circuit whose function is switched to a change function mode different from the normal operation mode by input of a switch signal, a measuring instrument for detecting an output signal of the internal circuit in the change function mode, and the like. An electronic circuit having an output terminal to which an external circuit is connected, a power supply for supplying a current to the output terminal through a resistor having a predetermined size, and a predetermined voltage when the external circuit is connected to the output terminal. An electronic circuit having a mode-changeable internal circuit, comprising: a switching circuit having a switching signal output circuit for detecting a voltage value of an output terminal falling to a value and outputting the switching signal to the internal circuit. circuit. 2. An internal circuit whose function is switched to a plurality of changed function modes different from the normal operation mode in accordance with a plurality of kinds of switching signals, and an output of the internal circuit in the changed function mode is supplied. And an electronic circuit having an output terminal to which an external circuit is connected; and a power supply for supplying a current to the output terminal via a resistor having a predetermined size.
When the external circuit is connected to the output terminal, the magnitude of the voltage value of the output terminal which falls to a predetermined value depending on the magnitude of the resistance of the external circuit is detected, and the magnitude of the voltage value is determined in accordance with the magnitude of the voltage value. And a switching circuit having a plurality of switching signal output circuits for outputting different switching signals.