JPH019983Y2 - - Google Patents

Description

[Detailed Description of the Invention] Field of the Invention The present invention relates to a power outage guarantee circuit for a display terminal device, such as an electric display that displays traffic conditions on major roads, which is characterized by data retention in the event of a power outage. It is something.

Prior Art and its Problems In a display terminal device such as an electronic display device, display data transmitted from a center is held in a temporary display buffer, and the display is displayed based on the data in this buffer. It is designed to be driven to perform display operations. However, if the contents of the terminal device's display buffer were damaged due to a power outage, the display data had to be retransmitted. Therefore, when there is a large amount of display data, there is a drawback that it takes time to recover the display. Road information display systems and the like that are comprised of many display terminal devices have had problems in that confusion occurs during power outages and the system becomes unstable.

Purpose of the invention The present invention is to solve these conventional problems, and is to provide a display terminal that retains the memory contents of the display buffer in the event of an instantaneous power outage, and does not require retransmission of display data. The purpose is to provide a power outage guarantee circuit for equipment.

Structure and Effects of the Invention The present invention is a display terminal device having a display information storage means for temporarily holding display data transmitted from a center, and a display section that displays according to the display information storage means, A data guarantee circuit that retains the memory contents of the storage means for a predetermined time in the event of a power outage, a timer means whose operating time is less than the data guarantee time of the guarantee circuit, and retransmission of display data to the center only in the event of a power outage that is longer than the operating time of the timer means. The present invention is characterized by comprising a control means for determining.

According to the present invention having such features, there is no need to resend display data in the event of an instantaneous power outage, and display can be resumed immediately as necessary after power outage is restored. Therefore, the interruption of display can be shortened, and the reliability of the device can be improved. Furthermore, in a system consisting of a large number of display devices, there is no risk of confusion even if there is a momentary power outage, and the system can be operated efficiently.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a block diagram showing the electrical configuration of a display terminal device showing an embodiment of the present invention. In this embodiment, it is assumed that the terminal device is an electronic display device that reports road information and the like. In this figure, a terminal device 1 is connected to a center 2 via a data transmission line. The terminal device 1 has a central processing unit, a control section 3 that controls each part of the terminal device 1 according to signals from the center 2, and a display information buffer 4 that holds display data given from the center 2. There is. The output of the display information buffer 4 is applied to an electronic display board 5 serving as a display section for display. In the present invention, a guarantee circuit 6 is connected to the display information buffer 4 to temporarily hold the data in the event of a power outage. The guarantee circuit 6 is a backup circuit using a battery, and the data in the display information buffer 4 can be reliably held only for a certain guarantee time Tb. Furthermore, in this invention, a power outage detection timer 7 is used to detect power outage time.
is provided. The power failure detection timer 7 has a discharge circuit, such as a CR type discharge circuit, which is connected to the power supply circuit and has a predetermined time constant, and a level discriminator that discriminates its output voltage level, and its detection output is given to the control unit 3. . The timer time Ta of the power failure detection timer 7 is set to be slightly shorter than the guaranteed time Tb of the guarantee circuit 6.

Next, the operation of this embodiment will be explained with reference to the waveform diagram of FIG. 2. Display information is now sent from the center 2 to this terminal device 1 and stored in the display information buffer 4 via the control section 3, and is displayed on the electronic display board 5 by a command from the center 2 or under the control of the control section 3. shall be displayed on the page. Now suppose that there is an instantaneous power outage between times t1 and t2. If this power outage time T is shorter than the timer time Ta of the power outage detection timer 7, as shown in FIG. The output from timer 7 does not stop. Therefore, Figure 2e
As shown in the figure, the data in the display information buffer 4 is retained as is even if this power outage occurs. Therefore, when the power outage is restored, the data can be displayed continuously as shown in FIG. 2f without requiring the center 2 to resend the display data. However, if there is a power outage between times t3 and t6, and this power outage time T is longer than the timer time Ta of the power outage detection timer 7, then
As shown in FIG. 2 b and c, the level of the discharge circuit of timer 7 becomes lower than the detection level of the timer output shown by the broken line in FIG. 2 b at time t4, and as shown in FIG. stops. Subsequently, at time t5, the guarantee time of the guarantee circuit 6
Once Tb has elapsed, the data in the display information buffer 4 is no longer guaranteed by the guarantee circuit 6, as shown in FIG. 2d, and the display cannot continue even if the power outage is restored. Therefore, it is necessary to request the center 2 to resend the data as shown in FIG. 2f.

In this way, the timer time of the power failure detection timer 6 is used to determine whether or not to request the center 2 to retransmit data.

Although this embodiment has been described with respect to a display terminal device that displays road information, it goes without saying that the present invention can be applied to various other devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the display terminal device of the present invention, and FIG. 2 is a waveform diagram of each part showing its operation during a power outage. 1...Terminal device, 2...Center, 3...Control unit, 4...Display information buffer, 5...Electronic display board, 6...Guarantee circuit, 7...Power failure detection timer.

Claims (1)

[Scope of Claim for Utility Model Registration] In a display terminal device having a display information storage means for temporarily holding display data transmitted from a center and a display section that displays according to the display information storage means, in the event of a power outage, a data guarantee circuit that retains the memory contents of the storage means for a predetermined period of time; a timer means having an operation time that is less than or equal to the data guarantee time of the guarantee circuit; A power outage guarantee circuit for a display terminal device, comprising: a control means for requesting retransmission;