JPS63143619A - Automatic discriminating device for hot start and cold start - Google Patents

Abstract

PURPOSE:To automatically discriminate hot start or cold start by monitoring the voltage of a RAM power supply for the backup of a RAM and deciding whether data stored in the RAM is correct or not. CONSTITUTION:When the voltage value of the RAM backup power supply 6 maintains the memory holding/guaranteeing voltage of the RAM 3, hot start is executed. At the time of power failure, the voltage value of the power supply 6 is dropped and the memory holding/guaranteeing voltage of the RAM 3 can not be maintained. A voltage detecting circuit 7 detects the voltage drop of the power supply 6 and resets a flip flop 8. When the power failure is restored and a power ON reset circuit 5 releases a reset signal, a microcomputer (CPU) 1 starts its operation, and after checking the reset state of the flip flop 8, executes cold start. Since whether data in the RAM 3 are correct or not is not guaranteed, the contents of the RAM 3 are cleared, the flip flop 8 is set up and the succeeding programs are sequentially executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic hot start/cold start discrimination device that uses a microcomputer and is connected to a memory holding circuit that operates during a power outage in electronic equipment.

Conventional technology In recent years, microcomputers have been introduced into all types of equipment.
It is spreading rapidly.

Hot start 2 t-- in the conventional microcomputer peripheral circuit described above with reference to the drawings:
' and how to perform a cold start.

FIG. 2 is a block diagram of a basic circuit of a microcomputer showing a conventional cold start method. In Figure 2, 1 is a microcomputer (CPU), 2 is an RO
M, 311: RAM, 5U power-on reset circuit, 9
6 is a cold start switch, and 6 is a backup power supply to protect the RAM memory in the event of a power outage.

The operation of the basic circuit configuration diagram configured as described above will be described below.

When the power of the microcomputer 1 is turned on and the reset signal from the power-on reset circuit 6 is released, the microcomputer 1 starts executing the program from the unique start address of the microcomputer 1 and processes the instructions written in the ROM 2. I will do it. Such a start of execution of a program is generally called a hot start, and the tabulated data stored in the RAM 3 is usually used as is without being cleared. If you want to clear all the data in RAM 5 and start executing the program, press the cold start switch 9 while turning on the power, and a cold start signal will be sent to the interrupt input terminal via the AND gate circuit 10. The execution of the program starts from the interrupt processing program, where all the data in the RAM 3 is cleared, all the operations and states before the power outage are cleared, and the operation starts from the initial state. Such a start of program execution is generally called a cold start.

Problems to be Solved by the Invention However, with the above configuration, when performing a cold start, it is necessary to manually turn on the power while pressing the cold start switch 9. The problem with the data in the RAM 3 is that it is necessary for a person to actually operate the data and judge whether it is correct or not.

In view of the above problems, the present invention monitors the voltage of the RAM power supply for backing up the RAM and determines whether the data stored in the RAM is correct. The purpose is to automatically determine whether the

Means for Solving the Problems In order to solve the above problems, the hot start/cold start automatic discrimination circuit of the present invention detects whether the voltage of the RAM backup power supply is sufficient for memory retention. and means for selecting cold start or hot start of the microcomputer according to the detection output of the detection means.

Effect The present invention has the above-described configuration to reduce R consumed during a power outage.
A voltage value of a backup power source of the AM is detected, a detection means detects that the voltage of the backup power source has fallen below a memory retention voltage of the RAM during standby, and when the power is turned on, the detection output of the detection means indicates the memory retention voltage. If it shows that the voltage is above the voltage, the memory in the RAM is guaranteed to be correct, so a hot start is performed, and if it is below the holding voltage, it is not guaranteed that the memory in the RAM is correct. Therefore, it performs a cold start, and can automatically distinguish between a hot start and a cold start, eliminates the need for a manual cold start, and prevents malfunctions.

Embodiment Hereinafter, a hot start/cold start automatic discrimination circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a basic circuit diagram of a microcomputer in an embodiment of the present invention. In Figure 1, 1 is a microcomputer (CPU), 2 is a ROM, and 3 is an RA.
M, 4 is an input/output port, 5 is a power-on reset circuit,
e is a RAM backup power supply, 7 is a voltage detection circuit for detecting whether the voltage of the RAM backup power supply 6 maintains the memory retention guarantee voltage of the RAM 3;
8 is a flip-flop for storing the state of the voltage value of the backup power supply 6;
It is set after the start of the RAM buffer 6', and is reset when the voltage value of the pull-up power supply 6 falls below the memory retention guaranteed voltage value of RAM a.

The operation of the hot start/cold start automatic discrimination circuit configured as described above will be explained below with reference to FIG.

FIG. 1 is a basic circuit diagram of a microcomputer according to an embodiment of the present invention. When the power is turned on, the power-on reset circuit 5 releases the reset signal, and the microcomputer (CPU) 1 is activated. Execution starts from the unique address written in the ROM 2 according to the instructions written in the ROM 2. At this time, the microcomputer (CPU) 1 checks the state of the flip-flop 8 that stores the voltage value state of the RAM backup power supply 6, and if the flip-flop is set, the RAM backup power supply 6 Since the voltage value maintains the memory retention guaranteed voltage of RAM3, a hot start is performed. From now on, R
The programs written in OM2 are processed sequentially, but when a power outage occurs, the computer (CPU) stops L and RAM3
The data is protected by the RAM backup battery 6. However, the RAM backup power supply 6 wears out over time, the voltage value decreases, and finally,
The memory retention guarantee voltage of RAM3 cannot be maintained. The voltage detection circuit 7 detects a voltage drop in the RAM backup power supply 6 and resets the flip-flop 8.

Next, when the power is restored and the power-on reset circuit 5 releases the reset signal, the microcomputer (CPU)
1 starts operating, confirms that the state of the flip-flop is in the reset state, and performs a cold start. Since the data in RAM 5 is not guaranteed to be correct, clears the RAM 3 and resets the flip-flop. This program sets the program and executes subsequent programs in sequence.

After the microcomputer 1 is started, the flip-flop is set again.

Effects of the Invention As described above, the hot start/cold start automatic discrimination circuit of the present invention detects the voltage value of the RAM backup power supply and determines whether the voltage value maintains the memory retention guaranteed voltage of the RAM. By checking the status of the microcomputer (CPU) when the power is turned on,
It can automatically determine whether to perform a hot start or a cold start, eliminating the need for manual cold start operations, and even when performing a hot start, the data stored in the RAM is guaranteed to be correct. , malfunctions can be prevented. In addition, since cold start and hot start can be automatically selected, even if the device requires a large capacity power supply, by appropriately selecting the capacity of the RAM backup power supply, the apparent power outage retention time can be set for a long time. There is no need for the power supply circuit itself to take a long time to maintain the power outage, and costs can be reduced.

[Brief explanation of the drawing]

Figure 1 is a basic circuit configuration diagram of a microcomputer using an automatic hot start/cold start discrimination circuit according to an embodiment of the present invention, and Figures 29' and 29' are basic circuit configuration diagrams of a conventional microcomputer. . 1...Microcomputer (CPU), 2.
...ROM, 3...RAM, 4...
...Input/output port, 6...Power-on reset circuit, 6...Backup power supply for RAM, 7.
...Voltage detection circuit, 8...Flip-flop. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] means for detecting excess or deficiency of the memory retention voltage of the RAM;
An automatic hot start/cold start discrimination device having means for selectively switching whether or not to clear the memory contents in M.