JPS627219A - Signal output circuit - Google Patents

Abstract

PURPOSE:To obtain a signal output circuit preventing surely malfunction with simple circuit constitution by connecting a connection circuit comprising a Zener diode and a resistor connected between a power supply and common to one input of a gate circuit. CONSTITUTION:The Zener diode 5 connected to a logic power supply +5V and a resistor 6 whose one terminal is connected to common are connected to one input (2) of the gate 2 comprising an open collector TTL IC. When the voltage of the logic power supply drops and is lower than the voltage of the Zener diode 5, since th Zener diode 5 carries no current, the level of the terminal (2) of the gate 2 is kept to a low level and its output goes to a high level. Then even when the input signal goes to any level, the output is kept to the high state, that is, the state of absence of signal to prevent malfunction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to TTL oven collector I of floppy disk drive (FDI) devices, DISK devices, etc.
″11 UACTIVE L OW A CT I ■E
>Related to a signal output circuit when a device having an interface and a control circuit are operated in conjunction with each other using separate power supplies.

Conventional technology] Conventionally, circuits with such a control circuit and a drive device are generally operated by the same power source, so that the main body control section and the drive device side are turned on and off at the same time, thereby preventing malfunctions. If the logic voltage drops from +5V to some extent by the reset IC or reset control circuit (generally 4.3 to 4.0■)
, the interface circuit section was cut off to prevent malfunctions by making it non-active (no signal with the logic signal interface).

FIG. 2 shows an example of a conventional circuit, in which there are five TTL negative logic interfaces, a control circuit 10, a reset circuit 1, and a control circuit 10.
The gate circuit (7438) 2 connected thereto serves as an output circuit, and this output is connected to the input LSIB together with a resistor 1 connected to the 5V power supply of the drive device 12 via the interface circuit 1]-3.

[Problem that the invention seeks to solve]

In this way, in the conventional circuit, the power is turned on and
In order to prevent the storage medium from being destroyed by the write power supply due to malfunction in the unstable operation region when turned off, a dedicated reset circuit 1 is used in the main body monolithic drive circuit 10, resulting in a complicated circuit configuration.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a signal output circuit that is simple and can reliably prevent malfunctions.

[Means for solving problems]

The configuration of the signal output circuit of the present invention is configured by connecting a connection circuit of a Zener diode and a resistor connected between a power supply and ground to one input of a gate circuit of an open collector type driver, and the gate circuit One of the inputs is fixed at a low level to prevent malfunction.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, a Zener diode 5 connected to a logic power supply (+5V) and a resistor 6 whose one end is grounded are connected to one input (2) of a gate 2 consisting of an IC of an oven collector TTL. When the voltage of the logic power supply decreases and becomes lower than the voltage of the Zener diode 5, the Zener diode 5 does not shunt the current, so the terminal of the input gate 2 (
2) is held low and its output goes high.

Therefore, no matter what operation the input signal performs, the output is kept in the high or high state, that is, in the absence of a signal, to prevent malfunction. Gate 2 of this circuit is generally T
Using T L 7438 equivalent, Zener diode 5
As the voltage, a voltage as low as possible is used in view of the relationship with the high input voltage of the gate 2.

〔Effect of the invention〕

As explained above, the present invention can easily prevent malfunctions caused by power on/off in the relationship between the device main body and the input/output drive, which operate on separate power supplies, without adding a special circuit. At the same time, malfunctions can be reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram including a conventional signal output circuit. In the figure, 1...reset circuit, 2... game I-circuit (743
8), 3...LSI circuit, 4.6...resistance, 5...
・Zener diode, 10...control circuit, 11...
- Interface circuit, 12...Drive device. −°＼ 1 Shifuichi 2/ Figure 7? figure

Claims (1)

[Claims] The gate circuit of an open collector type driver is configured by connecting a connection circuit consisting of a Zener diode and a resistor connected between the power supply and ground to one input of the gate circuit, and fixing one input of the gate circuit to a low level to prevent malfunction. A signal output circuit characterized by preventing.