JPH06242849A - Power source abnormality detecting circuit in information transfer device - Google Patents

Abstract

PURPOSE:To easily execute both of an information transfer between microcomputers and a power source abnormality detection by using one piece of D/A output transmission line in common without increasing the number of pins of a connector. CONSTITUTION:Information from a first microcomputer 1 is transferred to a second microcomputer 4 through a transmission line 3 by a D/A output, and a partial charge of an information transfer of its D/A output is constituted of a VF voltage or above of a diode 11 in advance. This D/A output is fed back by an A/D input to a first microcomputer 1 through a resistance 10, and also, connected to a power source circuit 6 through the diode 11. When a voltage of the power source circuit 6 becomes zero, a feedback A/D input becomes the VF voltage, and since it is set originally to the VF voltage or above, it is decided that a power supply voltage is abnormal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for detecting a power failure of a device such as a magnetic recording / reproducing device for transmitting information such as control signals between microcomputers.

[0002]

2. Description of the Related Art FIG. 2 is a block circuit diagram for transmitting information and detecting a power supply voltage in a conventional magnetic recording / reproducing apparatus. 1 is a microcomputer that outputs digital signals corresponding to various control signals as an information source, and 2 is D
The / A conversion circuit converts the digital signal output of the microcomputer 1 into an analog signal and transmits the information to the next stage through the transmission line 3. Reference numeral 4 is a microcomputer for receiving information, and 5 is an A / D conversion circuit for converting an analog signal of the transmission line 3 into a digital signal.
To enter. 6 is a power supply circuit, which is a microcomputer
4. Supply an operating voltage to the A / D conversion circuit 5. A voltage detection circuit 7 detects the voltage of the power supply circuit 6 through the transmission line 8 and inputs the detection output to the microcomputer 4. Here, the microcomputer 1, the D / A conversion circuit 2, and the voltage detection circuit 7 constitute an information transmission circuit block T, and the microcomputer 4, the A / D conversion circuit 5, and the power supply circuit 6 are provided with information. The receiving circuit block R is configured.

In such a configuration, the digital signal from the microcomputer 1 of the information transmission circuit block T is converted into an analog signal by the D / A conversion circuit 2,
It is transmitted to the information receiving circuit block R side through the transmission line 3. In the information receiving circuit block R, the transmitted analog signal is converted into a digital signal again by the A / D conversion circuit 5, and the digital signal is input to the microcomputer 4. On the other hand, the voltage detection circuit 7 of the information transmission circuit block T constantly monitors the voltage of the power supply circuit 6 on the information reception circuit block R side through the transmission line 8 and informs the microcomputer 1 whether this voltage is normal or not. Inform.

[0004]

The information transmission device in the conventional magnetic recording device is configured as described above.
In order to detect the voltage abnormality of the power supply circuit 6 of the information receiving circuit block R, it is necessary to provide the voltage detecting circuit 7 in the information transmitting circuit block T and connect it to the power supply circuit 6 through the transmission line. Therefore, when the information transmission circuit block T and the information reception circuit block R are separated via the connector, a new connector pin is required for detecting the voltage abnormality of the power supply circuit 6, which increases the space of the printed circuit board. However, if the number of pins of the connector cannot be increased due to the space of the printed circuit board, there is a problem that such a power supply abnormality detection circuit cannot be configured.

The present invention has been made in order to solve the above-mentioned problems, and a connector is provided for an information transmission device for transmitting information between microcomputers by A / D output and D / A input. Provided is a power supply abnormality detection circuit which can easily detect a power supply abnormality without increasing the number of pins.

[0006]

According to the present invention, there is provided an information transmission circuit block including a first microcomputer for outputting a digital signal and a D / A conversion circuit for converting the digital signal into an analog signal and transmitting the analog signal. And an A / D conversion circuit connected to the D / A conversion circuit of the information transmission circuit block via a transmission line, a second microcomputer to which the analog signal output thereof is input, and a power supply circuit for operating these. In an information transmission device including an information reception circuit block including a signal transmission circuit block, an input terminal of the information transmission circuit block is connected to the transmission line, and a digital signal output of the D / A conversion circuit is converted into an analog signal. A / D for return to 1 microcomputer
A conversion circuit is provided, and a diode is connected between the input terminal of the feedback A / D conversion circuit and the power supply circuit of the information receiving circuit block so as to be conductive when the power supply circuit is abnormal.

[0007]

When the voltage of the power supply circuit in the information receiving circuit block decreases, the diode becomes conductive, and the output voltage of the D / A conversion circuit drops to the power supply circuit through the diode. Therefore, the input of the feedback A / D conversion circuit The voltage drops to the diode forward voltage VF. This voltage information is for feedback A
The signal is converted into a digital signal by the / D conversion circuit and fed back to the microcomputer 1, and the microcomputer determines that the power supply circuit is abnormal.

[0008]

【Example】

Example 1. FIG. 1 is a block circuit diagram of an information transmitting device in a magnetic recording / reproducing device showing an embodiment of the present invention. In the figure, 1 to 6 are the same as those shown in FIG. 2, 9 is a feedback A / D conversion circuit, the input end of which is connected to the transmission line 3 via a resistor 10, and the D / A conversion circuit The digital signal output of 2 is converted into an analog signal and fed back to the first microcomputer 1. 11 is a diode,
It is connected between the input terminal of the feedback A / D conversion circuit 9 and the power supply circuit 6 in a direction opposite to the voltage of the power supply circuit.

Next, the operation will be described. The transmission of information from the microcomputer 1 of the information transmitting circuit block T to the microcomputer 4 of the information receiving circuit block R is the same as in the case of FIG. D of the information transmission circuit block T
The digital signal output from the A / A conversion circuit 2 is transmitted through the transmission line 3 to the A / D conversion circuit 5 of the information reception circuit block R.
At the same time, it is input to the feedback A / D conversion circuit 9 via the resistor 10. Here diode the output of the D / A conversion circuit 2 - If left to perform communication at a higher voltage than the forward voltage V _F of the de 11, the voltage of the power supply circuit 6 has risen sufficiently diode - de 11 Is off,
The output voltage of the D / A conversion circuit 2 is input to the feedback A / D conversion circuit 9 via the resistor 10 in the same voltage. This time is normal.

Next, the voltage of the power supply circuit 6 does not rise,
In the zero potential state, the diode 11 becomes conductive, and the output voltage of the D / A conversion circuit 2 passes through the resistor 10 and then falls to the power supply circuit 6 through the diode 11, so that the feedback A / input voltage of the D conversion circuit 9 diode - the de of the forward voltage V _F. This voltage information is used for feedback A / D
When it is converted into a digital signal by the conversion circuit 9 and returned to the microcomputer 1, the microcomputer 1 compares the data to be sent and the received data, and there is a difference between the two. , It is determined that the power supply circuit 6 is abnormal.

[0011]

As described above, according to the present invention, since information transmission and power supply abnormality detection are performed by using one transmission line for D / A output, the information transmission circuit block is used for feedback. Since it is only necessary to provide an A / D conversion circuit, there is no need to provide a power supply voltage detection circuit as in the past, so there is no need to increase the number of pins on the connector.
It is possible to easily detect a power supply abnormality of a device that transmits information between computers, and as a result, it is possible to save the space of the printed circuit board.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a conventional example.

[Explanation of symbols]

 T ... Information transmitting circuit block R ... Information receiving circuit block 1 ... Microcomputer 2 ... D / A conversion circuit 3 ... Transmission line 4 ... Microcomputer 5 ... .A / D conversion circuit 6 ... power supply circuit 9 ... feedback A / D conversion circuit 10 ... resistor 11 ... diode

Claims (2)

[Claims] 1. An information transmission circuit block including a first microcomputer for outputting a digital signal and a D / A conversion circuit for converting the digital signal into an analog signal and transmitting the analog signal, and D of the information transmission circuit block. An information receiving circuit block including an A / D conversion circuit connected to the A / A conversion circuit via a transmission line, a second microcomputer to which an analog signal output of the A / D conversion circuit is input, and a power supply circuit for operating these circuits. In the information transmission device,
An input terminal of the information transmission circuit block is connected to the transmission line, and a feedback A / D conversion circuit for converting the digital signal output of the D / A conversion circuit into an analog signal and feeding it back to the first microcomputer. Along with
A power supply abnormality of the information transmission device characterized in that a diode is connected between the input terminal of the feedback A / D conversion circuit and the power supply circuit of the information receiving circuit block so as to conduct when the power supply circuit is abnormal. Detection circuit. 2. The input terminal of the feedback A / D conversion circuit according to claim 1, wherein the diode is connected in a direction opposite to the voltage of the power supply circuit while connecting the input end to the transmission line via a resistor. A power supply abnormality detection circuit for an information transmission device, characterized in that the power supply abnormality detection circuit is connected to.