JPS60214032A - Setting device for initial condition - Google Patents

Abstract

PURPOSE:To decrease the number of components by forming the voltage comparator of an initial condition setting circuit for a digital circuit in the same integrated circuit as the digital circuit. CONSTITUTION:The digital circuit 1 and voltage comparator 3 are constituted on the same chip to form the integrated circuit 11. An input changeover switch 12 operates to connect an external initial setting voltage input in the power- on time of the digital circuit 1 to the voltage comparator 3 or an external initial setting circuit 13 provided outside of the integrated circuit 11. When the input changeover switch 12 is connected to the voltage comparator 3, the external initial setting circuit 13 is unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an initial condition setting device used in a digital circuit or the like to set initial conditions when power is turned on.

The configuration of the conventional example and its problems An example of a conventional initial condition setting device for a digital circuit is shown in the first example.
As shown in the figure.

In the figure, 1 is a digital circuit, 2 is a voltage input terminal for setting its initial conditions, and 3 is a voltage comparator.Resistors 4 to 6 and a Zener diode 7 are connected to the input terminals of the voltage comparator 3. The output is connected to an input voltage terminal (hereinafter abbreviated as R8T) 2 for initial condition setting of the digital circuit 1.

Its operation will be explained with reference to FIG. The horizontal axis of the figure is time, and the vertical axis is voltage. In the figure, A is the rise characteristic when the power supply 8 is turned on, and at time to, the steady voltage voltage B
(V). A in B is a characteristic of the + side input terminal 9 of the voltage comparator 3, and is a voltage value obtained by dividing the voltage of the person's power supply 8 by a resistor of 4.5 degrees at each time. In steady state, it is vA. It is assumed that b of B is the characteristic of the one-side input terminal 10 of the voltage comparator 3, and the voltage of the Zener diode 7 in a steady state is vB. Until the voltage of the Zener diode 7 reaches vB at the rise of the power supply 8, that is, until time t1, b of B has the same characteristics as A, but after t, it becomes a constant voltage VB.

If vB is set lower than vA, a between time t1 and to
An intersection of and b occurs. Let this time be kt2.

If the voltage of the power supply 8 at time t2 is a value that allows the digital circuit 1 to operate normally, then the initial settings are made at this point, that is, the circuit is set to the initial operating conditions, and the operation of the digital circuit 1, which had been prohibited until then, is stopped. Let it start. It is assumed that the digital circuit 1 is configured to perform R3T2 during the operation inhibit period. In this case, R3' before time t2
When an input as shown in FIG. 2B is applied to the terminal voltage comparator 3 of T2, such an output is obtained. That is, time t
2, the voltage is L'', and after that, the characteristics of the power supply 8 are almost the same as those of the power source 8.If the output of the voltage comparator 3, such as this characteristic C, is coupled to I'tST2 of the digital circuit 1, the purpose can be achieved. It will be done.

When considering a microcomputer as a digital circuit, until now, many processes such as NMO8 cannot incorporate a voltage comparator, and therefore a voltage comparator 3 has been used separately from the microcomputer.

However, recently, microcomputers are increasingly being configured with 0MO8.

In this case, since the process allows for a complementary configuration, it is possible to create the voltage comparator 3 on the same chip as the microcomputer. Although it is preferable to do so in order to reduce the number of parts, when replacing an NMOS microcomputer with the same function with a CMOS microcomputer for the purpose of reducing power consumption, it is recommended to do so if the initial conditions are set differently. This is not possible and is inconvenient.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an initial condition setting circuit for use in a digital circuit with a built-in initial condition setting circuit, which eliminates the above-mentioned drawbacks and allows the use of conventional external initial condition setting circuits.

Structure of the Invention The initial condition setting device according to the present invention inputs a voltage input for initial condition setting at power-on of an integrated digital circuit to a voltage comparator provided on the same chip as the integrated circuit. It is configured to have a switch that can switch between connecting the integrated circuit and connecting it to a voltage input terminal from outside the integrated circuit.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

In FIG. 3, parts common to those in FIG. 1 are given the same numbers.

Reference numeral 11 denotes an integrated circuit in which a digital circuit 1, a voltage ratio 1, and a comparator 3 are constructed on the same chip.

12 is the input selector switch of R8T2, 13 is the integrated circuit 1
An external initialization circuit 14 is a voltage input terminal from outside the integrated circuit. This output and voltage comparator 3
The outputs of both have similar characteristics, as shown in FIG. 2C. Its operation is the same as the conventional example.

When the input selector switch 12 of R8T2 is connected to the voltage comparator 3, the external initial setting circuit 13 is not necessary, and the initial conditions are determined by the resistors 4 to 6 and the Zener diode 7.

Although this usage is originally intended, if you simply want to replace the conventional integrated circuit 1 with this integrated circuit 11, switch 1
2 is connected to the external initial condition setting circuit 13 side. In this case, the inputs 9 and 1o of the voltage comparator 3 are arranged so as to be connected to conventionally vacant pins. Also, resistors 4 to 6,
Zener diode 7 is not required. The input changeover switch 12 is realized by changing the connection of conductors within the integrated circuit 11.

Effects of the Invention As described above, according to the present invention, since the voltage comparator of the initial condition setting circuit of the digital circuit is formed in the same integrated circuit as the digital circuit, the number of parts can be reduced.
Furthermore, even if it is difficult to change the peripheral circuitry when replacing a conventionally used digital integrated circuit, this can be easily done by changing a switch.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of a conventional initial condition setting device for a digital circuit, Fig. 2 A, B, and C are waveform diagrams for explaining the operation of the initial condition setting device, and Fig. 3 is an embodiment of the present invention. FIG. 2 is a wiring diagram of an initial condition setting device in FIG. 1... Digital circuit, 2... Voltage input terminal for initial condition setting (R8T), 3... Voltage comparator, 8... Power supply voltage, 11... integrated circuit,
12...Switch, 13...External initial setting circuit, 14...Voltage input terminal from outside the integrated circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] Connect the voltage input for initial condition setting at 9 o'clock when the power supply of the integrated digital circuit is turned on to the voltage comparator output provided on the same chip as this integrated circuit, or connect it to the voltage input terminal from outside the integrated circuit. An initial condition setting device characterized in that it is provided with a switch that can switch whether to connect to or not.