JPH0119479Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to an in-vehicle wireless communication device that controls the continuation of a communication state when the power is momentarily cut off during communication.

[Description of prior art]

In-vehicle communication devices use a battery as a power source, so the power supply voltage may drop momentarily due to starter drive or the like, or in some cases, a momentary power outage may occur.

As a countermeasure against momentary power interruptions for communication devices connected to such unstable power sources, a circuit that generates a reset signal to prevent the microprocessor built into the communication device from going out of control in the event of a momentary power interruption is required. is provided.

Although this is a sufficient measure to prevent the microprocessor from running out of control, it has the disadvantage that if the communication device is reset due to a momentary power interruption while it is in the communication state, the communication state returns to the initial state. There is.

Another countermeasure is to insert a large-capacity capacitor into the power supply circuit and supply the stored power in the event of a momentary power outage to maintain the normal power supply state, but devices that require power cannot be controlled. It is necessary not only for circuits but also for wireless circuits such as transmitters. During communication, this transmitter is naturally in operation and a current of several amperes is flowing, so the withstand voltage is 35V ~
Even with a large-capacity electrolytic capacitor of about 50V, it is difficult to maintain power during a momentary power outage. In this case, if you do not cover momentary power interruptions in the power supply to the wireless circuit,
The synthesizer circuit in the wireless circuit section malfunctions,
This causes problems such as loss of frequency locking.

The inventor has developed a circuit configuration that includes a rewritable memory with low current consumption, a large-capacity capacitor, and a time constant circuit that detects the length of the power-off time to prevent instantaneous power outages during communication. We focused on what could be done and completed the present invention.

[Purpose of invention]

The present invention enables the communication state to return to the initial state by a reset signal even if the power supply voltage of the vehicle-mounted wireless communication device is momentarily interrupted for a short period of time without any substantial problem.
It is an object of the present invention to provide an in-vehicle wireless communication device that can prevent malfunction of a wireless circuit and frequency locking due to a power-off state, and can maintain a normal communication state.

[Characteristics of the invention]

The present invention provides a wireless communication device that includes a wireless communication circuit, a microprocessor that controls the wireless communication circuit, and a rewritable memory that is connected to the microprocessor and stores communication setting conditions. A time constant circuit that is equipped with a capacitor connected to the power circuit to hold the power supply voltage in the event of a momentary power interruption, holds the voltage when power is supplied, and discharges at a predetermined speed when the power is cut off; and this time constant circuit. and a buffer circuit whose input is connected to the control terminal of the microprocessor and whose output is connected to the control terminal of the microprocessor, and the microprocessor can reset after a momentary power interruption as long as a predetermined voltage is applied to the control terminal. It is characterized in that it is configured to continue communication according to the contents of the memory without any interruption, and is characterized in that even if there is a momentary power interruption in the communication state, it performs control to immediately return to the normal communication state.

[Explanation based on examples]

Next, an embodiment of the present invention will be explained based on the drawings.

FIG. 1 is a circuit configuration block diagram of an embodiment of the present invention, and FIG. 2 is a control flowchart of the embodiment of the present invention.

In the device according to the embodiment of the present invention, a microprocessor 2 that controls a wireless communication circuit 1 has a rewritable memory 3 (having a CMOS structure) that stores communication setting conditions.
RAM) and a time constant circuit 4 consisting of a resistor R1 and a capacitor C1 are connected which hold a voltage while power is being supplied and discharge at a predetermined speed when the power is cut off.

This time constant circuit 4 is connected to the control terminal P1 of the microprocessor 2 via a buffer circuit 5. A capacitor c2 is connected to the power supply circuits of the memory 3 and the buffer circuit 5 to hold the power supply voltage in the event of a momentary power interruption, and the microprocessor 2 is configured to receive a reset signal from the reset terminal RE.

The operation of the apparatus according to the embodiment of the present invention constructed as described above will be explained. When the power supply is momentarily cut off, a reset signal is output from a circuit not shown in the figure and is input to the reset terminal RE of the microprocessor 2, causing the power supply + _Vcc to drop to the ground level. 3 and batshua 5
Power continues to be supplied to the memory 3, and the contents stored in the memory 3 are retained even if the power is momentarily interrupted.

On the other hand, the output of the buffer 5, that is, the signal at the input port P1 of the microprocessor 2, is at the logic level "L" when the power is turned on, since it takes time for the capacitor C1 to be charged if it is not charged. and “H” when charged
level. The time it takes to change from “L” level to “H” level is the resistance R1 and capacitor C2.
determined by the time constant of

Therefore, when the power supply + _Vcc is once disconnected and then reconnected, if the input port P1 of the microprocessor 2 is at "H" level, the capacitor C1
Since the charge remains, the power-off time is short, and if P1 is at "L" level, it is determined that the power-off time is long.

On the other hand, the memory 3 stores information on whether or not the communication was in progress and on what radio frequency the communication was being performed, so when a reset signal is input to the microprocessor 2, as shown in FIG. The memory 3 determines whether or not the device is in a communication state, and if it is not in a communication state, it is initialized by reset and enters a standby state.

If it is in the communication state, then it is determined whether the power-off time is short or not based on the output of the time constant circuit 4.
If the power-off time is long, initial settings are made by reset and the device goes into standby mode; if it is determined that the power-off time is short, the radio frequency used last time is confirmed and that frequency is set in the memory 3. The communication state can be maintained by a transmission-on command.

[Effect of idea]

As described above, according to the present invention, by providing a buffer circuit, a time constant circuit composed of a resistor and a capacitor, a circuit having a memory and a capacitor for holding a power supply, it is possible to use a circuit that is practically harmless during communication. Even if there is a momentary power outage, it is possible to maintain the communication state without immediately returning the communication state to the initial state using a reset signal, and it is also possible to prevent malfunction of the radio circuit and frequency locking. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration block diagram of an embodiment of the present invention, and FIG. 2 is a control flowchart of the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Wireless communication circuit, 2... Microprocessor, 3... Memory, 4... Time constant circuit, 5... Buffer circuit, C1, C2... Capacitor, R1...
…resistance.

Claims (1)

[Claims for Utility Model Registration] A wireless communication device comprising a wireless communication circuit, a microprocessor that controls the wireless communication circuit, and a rewritable memory that is connected to the microprocessor and stores communication setting conditions. a time constant circuit that is connected to the power supply circuit of the memory and includes a capacitor for holding the power supply voltage in the event of a momentary power interruption, and that holds the voltage when the power is supplied and discharges at a predetermined speed when the power is cut off; and a buffer circuit whose input is connected to the time constant circuit and whose output is connected to the control terminal of the microprocessor, and the microprocessor is capable of handling instantaneous power interruptions as long as a predetermined voltage is applied to the control terminal. A wireless communication device characterized in that it is configured to perform control to continue communication according to the contents of the memory without performing a subsequent reset.