JP2003141097A - Non-volatile one-chip microcomputer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-volatile one-chip microcomputer in which the terminal specifications are made uniform to those of a mask ROM plate by using a second power supply terminal special for an internal circuit both as a reload power supply terminal and a general terminal. SOLUTION: This non-volatile one-chip microcomputer is provided with a power supply switching circuit 4 taking the voltage of a first power supply terminal VDD1 and a second power supply terminal VDD2 as input, taking the voltage of the second power supply terminal as a power supply switching input, and controlled by a control signal of the internal circuit, a level shifter incorporated I/O control circuit 1 taking the input voltage of the first power supply terminal and the output of the power supply switching circuit as a power supply, and having the second power supply terminal connected as an input/ output terminal, and another level shifter incorporated I/O control circuit 6 having an input/output terminal 5 connected. The power supply circuit switches 2 input according to the voltage of the second power supply terminal to be output as the power supply of the internal circuit. An input/output signal of each level shifter incorporated I/O control circuit is connected to the internal circuit as an input/output signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonvolatile one-chip microcomputer having control means for selecting a power supply terminal.

[0002]

2. Description of the Related Art A block diagram of a conventional one-chip microcomputer is shown in FIG. In the figure, the nonvolatile one-chip microcomputer 33 includes an I / O control circuit 31 with a built-in level shifter and other internal circuits 32. The I / O control circuit 31 has a dedicated first power supply terminal VD
It is connected to D1 and the second power supply terminal VDD2. The internal circuit 32 is connected to the second power supply terminal VDD2. The input / output terminal 34 of the one-chip microcomputer 33 is connected to the I / O control circuit 31,
The control circuit 31 and the internal circuit 32 communicate with the input / output signal line S.
Give and receive 31. The second power supply terminal VDD2 functions only as a power supply dedicated to the internal circuit 32.

[0003]

However, the non-volatile one-chip microcomputer 33 having the two power source terminals of the first power source terminal VDD1 and the second power source terminal VDD2 has the following problems. It was That is, the mask ROM version, which does not require electrical rewriting, requires the second power supply terminal VDD2 as a power source exclusively for rewriting, which is not necessary, so that it is not possible to configure a one-terminal power supply equivalent to the mask ROM version. . As a result, compared to the mask ROM version, the number of I / O terminals is reduced by one to secure the second power supply terminal, and the same terminal specifications cannot be achieved.

In particular, in a mask ROM version one-chip microcomputer having a small number of terminals, there are cases where all the general-purpose input / output terminals are used, so that a small number of terminals may be used for some applications.
Even if a soft bug occurs in M, it cannot be replaced with a non-volatile one-chip microcomputer with different terminal specifications.

The present invention has been made to solve such a problem, and in a one-chip microcomputer with a built-in power supply switching circuit, the second power supply terminal dedicated to the internal circuit is also used as a rewriting power supply terminal and a general-purpose terminal. By making it possible, it is an object to provide a non-volatile one-chip microcomputer having the same terminal specifications as those of the mask ROM version.

[0006]

A nonvolatile one-chip microcomputer according to the present invention comprises a first power supply terminal dedicated to an I / O control circuit and a second power supply dedicated to an internal circuit excluding the I / O control circuit. Assuming a configuration including a terminal and a predetermined number of input / output terminals, the voltages of the first power supply terminal and the second power supply terminal are used as inputs, and the voltage of the second power supply terminal is used as power supply switching input. A power supply switching circuit controlled by a control signal of the internal circuit, the input voltage of the first power supply terminal and the output of the power supply switching circuit as power supplies, and the second power supply terminal is the nonvolatile one-chip microcomputer Of the non-volatile one-chip microcomputer using the I / O control circuit with a built-in level shifter connected as an input / output terminal, the input voltage of the first power supply terminal, and the output of the power supply switching circuit as power sources. And a further level shifter internal I / O control circuit whose output terminal is connected. The power supply switching circuit switches and outputs the two inputs according to the voltage of the second power supply terminal supplied as the power supply switching input, and the output is connected as the power supply of the internal circuit. The input / output signals of the I / O control circuits with built-in level shifters are connected to the internal circuits as input / output signals.

According to this structure, the power supply switching circuit switches between the two power supplies, the first power supply terminal and the second power supply terminal, and when rewriting, the voltage of the second power supply terminal is exclusively used for rewriting as the power supply of the internal circuit. It is supplied as a power source, and at the time of reading, the voltage of the first power source terminal is supplied as a power source for the internal circuit. As a result, the second power supply terminal can be switched to a general-purpose input / output terminal of the one-chip microcomputer other than the power supply terminal, and the terminals can be used in common.

In addition, a nonvolatile one-chip microcomputer having another configuration of the present invention is a power supply comparison device which receives the voltages of the first power supply terminal and the second power supply terminal as inputs and is controlled by a control signal of the internal circuit. A circuit, using the input voltage of the first power supply terminal and the output of the power supply comparison circuit as power supplies,
An I / O control circuit with a built-in level shifter, in which the second power supply terminal is connected as an input / output terminal of the nonvolatile one-chip microcomputer, and an input voltage of the first power supply terminal and an output of the power supply comparison circuit are used as power supplies. , Another I / O control circuit with a built-in level shifter, to which the input / output terminals of the nonvolatile one-chip microcomputer are connected.
The power supply comparison circuit compares the respective voltages of the first power supply terminal and the second power supply terminal, outputs one of the two inputs according to the comparison result, and the output serves as the power supply of the internal circuit. Connected. The input / output signals of the I / O control circuits with built-in level shifters are connected to the internal circuits as input / output signals.

By using the power supply comparison circuit as in this configuration, the following effects can be obtained in addition to the above effects. That is, at the time of reading, by operating under the condition of (voltage of set power supply terminal VDD1) <(voltage of internal power supply terminal VDD2), low voltage high speed operation can be realized.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a nonvolatile one-chip microcomputer 3 with a built-in power supply switching circuit according to the first embodiment. Reference numerals 1 and 6 are I / O control circuits with built-in level shifters, 2 is an internal circuit except the I / O control circuits with built-in level shifters 1 and 6, and 4 is a power supply switching circuit.

The power supply switching circuit 4 includes a first power supply terminal VDD
1 and the voltage of the second power supply terminal VDD2 are input. The output S1 of the power supply switching circuit 4 is supplied as the power supply of the internal circuit 2. The power supply switching circuit 4 is controlled by the control signal S2 from the internal circuit 2 and also has a second power supply terminal VDD.
The voltage of 2 is used as the power supply switching input.

The I / O control circuit 1 with a built-in level shifter has a voltage of the first power supply terminal VDD1 and an output S of the power supply switching circuit 4.
1 is used as the power source. The second power supply terminal VDD2 is also connected as an input / output terminal of the nonvolatile one-chip microcomputer 3 to the terminal of the level shifter built-in I / O control circuit 1, and the input / output signal S3 of the level shifter built-in I / O control circuit 1 is supplied. , Are connected to the internal circuit 2 as input / output signals.

Similarly, an I / O control circuit 6 with a built-in level shifter
Uses the voltage of the first power supply terminal VDD1 and the output S1 of the power supply switching circuit 4 as power supplies. Further, the general-purpose terminal 5 of the nonvolatile one-chip microcomputer 3 is connected as an input / output terminal of the level shifter built-in I / O control circuit 6, and the input / output signal S4 of the level shifter built-in I / O control circuit 6 is sent to the internal circuit 2. It is connected as an input / output signal.

The general-purpose terminals 5 are arbitrary general-purpose terminals, and a plurality of general-purpose terminals are provided for the number of terminals on the non-volatile one-chip microcomputer 3. Only the general-purpose terminal 5 will be described.

The operation of the nonvolatile one-chip microcomputer 3 with a built-in power supply switching circuit of the first embodiment configured as described above will be described separately for rewriting and reading. A timing chart of operation is shown in FIG. 2 separately for rewriting and reading.

First, the rewriting operation will be described. The power supply switching circuit 4 selects one of the input voltages of the first power supply terminal VDD1 and the second power supply terminal VDD2 as the output S1 according to the H or L level of the second power supply terminal VDD2. The control signal S2 from the internal circuit 2 is
At the initial value when the power is turned on, the power switching circuit 4 is set to operate.

When rewriting the nonvolatile memory incorporated in the set, rewriting is generally performed using an onboard serial writer. In this case, at the time of rewriting, the set power supply voltage is supplied to the first power supply terminal VDD1, and the rewrite power supply voltage is applied to the second power supply terminal VDD2 at power-on. The power supply switching circuit 4 recognizes that the voltage level of the second power supply terminal VDD2 is the H level because the voltage level of the second power supply terminal VDD2 is set to the rewrite power supply voltage.
The input voltage of the power supply terminal VDD2 is selected and output as the output S1. Thus, at the time of rewriting, the second power supply terminal VDD2 is supplied as the power supply voltage of the internal circuit 2.

The power supply switching timing on the one-chip microcomputer 3 is set from the terminal reset release at power-on to the oscillation stabilization waiting of the external self-excited oscillator before the non-volatile memory program is executed. It is set during the internal reset timing provided for this purpose.
Therefore, after the internal reset is released to wait for oscillation stabilization, the internal circuit 2 is powered by the power supply voltage VDD at the time of rewriting.
Since 2 is supplied, rewriting is executed.

Next, the read operation will be described.
When reading is executed, a set power supply voltage is supplied to the first power supply terminal VDD1, and an L level externally set is applied to the second power supply terminal VDD2 at power-on. The power supply switching circuit 4 has a second power supply terminal VDD.
The voltage level of 2 is recognized as the L level, and the first power supply terminal V
The input voltage of DD1 is selectively output as the output S1. Thus, at the time of reading, the power supply terminal VDD1 is supplied as the power supply voltage of the internal circuit 2.

The power supply switching timing is set to wait for the oscillation stabilization of the external self-excited oscillator after the terminal reset is released when the power is turned on, before the program of the nonvolatile memory is executed, as in the case of writing. It is set during the internal reset timing. Therefore, after releasing the internal reset for waiting for oscillation stabilization, the power supply of the internal circuit 2 is supplied with the power supply voltage VDD1 used in the set, so that the reading is executed.

The program of the non-volatile memory is set beforehand by the control signal S2 of the internal circuit 2 so as to selectively fix the output S1 of the power supply switching circuit 4 to the first power supply terminal VDD1. By being executed, the used power supply voltage VDD1 on the set is always supplied as the power supply of the internal circuit 2 regardless of the H or L level of the second power supply terminal VDD2.

After setting the power supply S1 of the internal circuit 2 to VDD1, the second power supply terminal VDD2 can be freely set as a terminal. As a result, the second power supply terminal VDD2 is
As the input / output terminal of the nonvolatile one-chip microcomputer 3, it is connected to the terminal of the level shifter built-in I / O control circuit 1. Since the input / output signal S3 of the I / O control circuit 1 with a built-in level shifter is connected to the internal circuit 2 as an input / output signal, the second power supply terminal VDD2 can be freely controlled as a general-purpose terminal by a program during reading, The same terminal specifications as the mask ROM version can be realized.

Similarly, the general-purpose terminal 5 of the nonvolatile one-chip microcomputer 3 is an I / O with a built-in level shifter.
Connected as a terminal of the control circuit 6, with built-in level shifter I
Since the input / output signal S4 of the / O control circuit 6 is connected to the internal circuit 2 as an input / output signal, it goes without saying that it can be freely controlled by a program as a general-purpose terminal.

(Second Embodiment) FIG. 3 shows a nonvolatile one-chip microcomputer 23 with a built-in power supply switching circuit according to a second embodiment. 21 and 26 are I / O control circuits with built-in level shifters, 22 is an internal circuit excluding the I / O control circuits with built-in level shifters 21 and 26, and 24 is a power supply comparison circuit.

The power supply comparison circuit 24 has a first power supply terminal VD.
The voltages of D1 and the second power supply terminal VDD2 are input. The output S21 of the power supply comparison circuit 24 is connected as a power supply of the internal circuit 22. The power supply comparison circuit 24 is the internal circuit 2
It is controlled by the control signal S22.

The I / O control circuit 21 with a built-in level shifter
Input voltage of the first power supply terminal VDD1 and the power supply comparison circuit 24
The output S21 of is used as a power source. Second power supply terminal VDD2
However, the I / O control circuit 21 with a built-in level shifter is used as an input / output terminal of the nonvolatile one-chip microcomputer 23.
I / O control circuit 2 with built-in level shifter
One input / output signal S23 is connected to the internal circuit 22 as an input / output signal.

Similarly, the level shifter built-in I / O control circuit 26 uses the input voltage of the first power supply terminal VDD1 and the output S21 of the power supply comparison circuit 24 as power supplies. The general-purpose terminal 25 of the nonvolatile one-chip microcomputer 23 is connected as a terminal of the level shifter built-in I / O control circuit 26, and the input / output signal S24 of the level shifter built-in I / O control circuit 26 is connected.
Are connected to the internal circuit 22 as input / output signals.

The general-purpose terminals 25 are arbitrary general-purpose terminals, and a plurality of general-purpose terminals 25 are provided for the number of terminals on the nonvolatile one-chip microcomputer 23. Here, in order to simplify the description, the general-purpose terminal will be described as the general-purpose terminal 25 only.

The operation of the nonvolatile one-chip microcomputer 23 with a built-in power supply switching circuit of the second embodiment configured as described above will be described separately for rewriting and reading. Timing charts of the operation are shown in FIGS. 4 and 5 separately for rewriting and reading.

First, the operation at the time of rewriting will be described. Generally, in a nonvolatile one-chip microcomputer, when rewriting data in a memory, it is necessary to apply a rewriting power supply voltage higher than a reading power supply voltage to the internal circuit 22 due to the characteristics of the nonvolatile memory. First power supply terminal V
The power supply comparison circuit 24, which receives two power supply terminals of DD1 and the second power supply terminal VDD2, compares each input voltage, and selectively outputs the power supply terminal having a high potential as the output S21.
The control signal S22 of the internal circuit 22 is set to operate the power supply comparison circuit 24 at the initial value when the power is turned on. When rewriting the nonvolatile memory built into the set, rewriting is generally performed using an onboard serial writer. During rewriting, the set power supply voltage is supplied to the first power supply terminal VDD1.
A power supply voltage for rewriting, which is generally higher than the power supply voltage VDD1 used in the set, is applied to the second power supply terminal VDD2 when the power is turned on. Since the power supply comparison circuit 24 selects a power supply terminal having a high power supply voltage from each power supply terminal, at the time of rewriting, the input voltage of the second power supply terminal VDD2 is selectively output as the output S21 and supplied as the power supply voltage of the internal circuit 22. To do.

The power supply switching timing is the internal reset timing provided for waiting for the oscillation stabilization of the external self-excited oscillator after the terminal reset is released when the power is turned on before the program of the nonvolatile memory is executed. Set during the period. Therefore, after the internal reset is released to wait for oscillation stabilization, the power supply voltage VDD2 at the time of rewriting is supplied to the power supply of the internal circuit 22, so that the rewriting is executed.

Next, the read operation will be described.
For the read operation, the voltage of the first power supply terminal VDD1 and the voltage of the second power supply terminal VDD2 (hereinafter referred to as VDD
1 and abbreviated to VDD2), the operation and effect at the time of reading are different depending on whether VDD1> VDD2 and VDD1 <VDD2. Therefore, each case will be described separately.

First, the case of VDD1> VDD2 will be described. A timing chart of the operation is shown in FIG.

At the time of reading, the first power supply terminal VDD
1 is supplied with a set power supply voltage, a second power supply terminal VDD2 is externally set to a voltage lower than that of the first power supply terminal VDD1, and is applied when the power supply is turned on. The power supply comparison circuit 24 is the first one having the higher potential of the above two inputs.
The voltage of the power supply terminal VDD1 is selected and output as the output S21. Therefore, at the time of reading, the voltage of the first power supply terminal VDD1 is input as the power supply voltage of the internal circuit 22.

The power supply switching timing is the same as that at the time of writing in order to wait for the oscillation stabilization of the external self-excited oscillator after the terminal reset is released when the power is turned on before the program of the nonvolatile memory is executed. It is set during the provided internal reset timing. Therefore, after the internal reset is released to wait for oscillation stabilization, the power supply of the internal circuit 22 is supplied with the power supply voltage VDD1 used in the set, so that the reading is executed. In order to program the non-volatile memory, the output S21 of the power supply comparison circuit 24 is previously supplied by the control signal S22 of the internal circuit 22 to the power supply terminal VDD.
By setting the direction to be selectively fixed to 1 and reading the program of the above memory, regardless of the H or L level of the second power supply terminal VDD2, it is always used as a power supply for the internal circuit 22 in the set. Power supply voltage VDD
1 is applied. Therefore, after the power supply S21 of the internal circuit 22 is set to VDD1, VDD2 can be freely set as a terminal.

At this time, the second power supply terminal VDD2 is connected to the terminal of the level shifter built-in I / O control circuit 21 as an input / output terminal of the nonvolatile one-chip microcomputer 23, and the input / output of the level shifter built-in I / O control circuit 21 is performed. The signal S23 is connected to the internal circuit 22 as an input / output signal. Therefore, at the time of reading, the program can freely set the second
The power supply terminal VDD2 can be controlled as a general-purpose terminal, and the same terminal specifications as the mask ROM version can be realized.

Similarly, the general-purpose terminal 25 of the nonvolatile one-chip microcomputer 23 has a level shifter built-in I.
Since it is connected as a terminal of the I / O control circuit 26 and the input / output signal S24 of the I / O control circuit 26 with a built-in level shifter is connected as an input / output signal to the internal circuit 22, it can be freely controlled by a program as a general-purpose terminal. Needless to say.

Next, the case where VDD1 <VDD2 will be described. The timing chart is shown in FIG. When reading is executed, the set power supply voltage is supplied to the first power supply terminal VDD1, and a voltage higher than that of the power supply terminal VDD1 is externally set to the second power supply terminal VDD2 and is applied when the power is turned on. . The power supply comparison circuit 24 selects and outputs, as the output S21, the voltage of the second power supply terminal VDD2 having the higher potential of the two inputs. Therefore, at the time of reading, the second power supply terminal VDD2 is input as the power supply voltage of the internal circuit 22.

The power supply switching timing is the same as that at the time of writing in order to wait for the oscillation stabilization of the external self-excited oscillator after releasing the terminal reset at the time of powering up before executing the program of the nonvolatile memory. It is set during the provided internal reset timing. Therefore, after the internal reset is released to wait for oscillation stabilization, the power supply of the internal circuit 22 is supplied with the power supply voltage VDD2 used in the set, so that the reading is executed. The general-purpose terminal 25 of the nonvolatile one-chip microcomputer 23 is connected as a terminal of the level shifter built-in I / O control circuit 26, and the input / output signal S24 of the level shifter built-in I / O control circuit 26 is connected to the internal circuit 22 as an input / output signal. Because
It goes without saying that it can be freely controlled by a program as a general-purpose terminal.

As described above, when VDD1 <VDD2, as a particularly effective effect, when it is desired to operate the nonvolatile one-chip microcomputer 23 at high speed on the low-voltage drive set while the power supply voltage VDD1 is low. In addition, the power supply of the internal circuit 22 that controls the operation at low voltage,
Since it can be set up to an arbitrary power supply voltage VDD2 higher than the low voltage VDD1, low voltage high speed operation can be realized.

[0042]

According to the present invention, the set power source terminal VDD1 and the rewriting power source terminal VDD2 are switched to be connected as the power source of the internal circuit and the power source terminal VD.
D2 is connected to the internal circuit through the I / O control circuit with a built-in level shifter. Then, at the time of rewriting, the power supply terminal VDD2 is supplied to the internal circuit as a power source exclusively for rewriting,
At the time of reading, the power supply terminal VDD1 can be supplied as the power supply of the internal circuit. Therefore, at the time of reading, by switching the power supply terminal VDD2 as a general-purpose input / output terminal of the one-chip microcomputer other than the power supply terminal, it is possible to serve as a terminal, and the same terminal specifications as the mask ROM version can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a nonvolatile one-chip microcomputer with a built-in power supply switching circuit according to a first embodiment of the present invention.

FIG. 2 is a timing chart of a rewrite operation (VDD2 = H) and a read operation (VDD2 = L) of the nonvolatile one-chip microcomputer shown in FIG.

FIG. 3 is a block diagram showing a nonvolatile one-chip microcomputer with a built-in power supply comparison circuit according to a second embodiment of the present invention.

4 is a timing chart of a rewrite operation (VDD2> VDD1) and a read operation (VDD2 <VDD1) of the nonvolatile one-chip microcomputer shown in FIG.

5 is a timing chart of a high-speed read operation (VDD2> VDD1) of the nonvolatile one-chip microcomputer shown in FIG.

FIG. 6 is a block diagram showing a conventional nonvolatile one-chip microcomputer.

[Explanation of symbols]

1 level shifter built-in I / O control circuit 2 Internal circuit 3 Nonvolatile one-chip microcomputer 4 power supply switching circuit 5 General-purpose terminals 6 Level shifter built-in I / O control circuit 21 I / O control circuit with built-in level shifter 22 Internal circuit 23 Non-volatile one-chip microcomputer 24 Power supply comparison circuit 25 General-purpose terminal 26 I / O control circuit with built-in level shifter 31 I / O control circuit with built-in level shifter 32 Internal circuit 33 Non-volatile one-chip microcomputer 34 I / O terminals S1 output S2 control signal S3 I / O signal S4 I / O signal S21 output S22 control signal S23 I / O signal S24 I / O signal S31 I / O signal VDD1 First power supply terminal VDD2 Second power supply terminal

Claims (2)

[Claims] 1. A non-volatile memory having a first power supply terminal dedicated to an I / O control circuit, a second power supply terminal dedicated to an internal circuit excluding the I / O control circuit, and a predetermined number of input / output terminals. In the one-chip microcomputer, the voltages of the first power supply terminal and the second power supply terminal are input, and the voltage of the second power supply terminal is used as a power supply switching input,
The power supply switching circuit controlled by the control signal of the internal circuit, the input voltage of the first power supply terminal and the output of the power supply switching circuit are used as power supplies, and the second power supply terminal is the nonvolatile one-chip microcomputer. An I / O control circuit with a built-in level shifter connected as an input / output terminal;
And an input / output terminal of the non-volatile one-chip microcomputer connected to the input voltage of the power supply terminal and the output of the power supply switching circuit, and another I / O control circuit with a built-in level shifter. , The two inputs are switched and output according to the voltage of the second power supply terminal supplied as the power supply switching input, and the output is connected as the power supply of the internal circuit, and the I / O control circuit with the built-in level shifter The non-volatile one-chip microcomputer characterized in that the input / output signal of is connected to the internal circuit as the input / output signal. 2. A non-volatile memory having a first power supply terminal dedicated to an I / O control circuit, a second power supply terminal dedicated to an internal circuit excluding the I / O control circuit, and a predetermined number of input / output terminals. In a one-chip microcomputer, a power supply comparison circuit controlled by a control signal of the internal circuit, using a voltage of the first power supply terminal and a voltage of the second power supply terminal as inputs, and an input voltage of the first power supply terminal An I / O control circuit with a built-in level shifter in which the output of the power supply comparison circuit is used as a power supply and the second power supply terminal is connected as an input / output terminal of the nonvolatile one-chip microcomputer; and an input voltage of the first power supply terminal. And another level built-in I having the output of the power supply comparison circuit as a power supply and connected to the input / output terminal of the nonvolatile one-chip microcomputer.
/ O control circuit, the power supply comparison circuit compares each voltage of the first power supply terminal and the second power supply terminal, and outputs one of the two inputs according to the comparison result, A non-volatile one-chip microcomputer in which an output is connected as a power source for the internal circuit, and an input / output signal of each of the level shifter built-in I / O control circuits is connected as an input / output signal to the internal circuit.