JPH083772B2 - Clock signal supply device for microcomputer system - Google Patents

Description

The present invention relates to a clock signal supply device for a microcomputer system, and more particularly to a clock signal supply device for a microcomputer system capable of supplying a clock signal at a predetermined timing to each functional block of the microcomputer system. Concerning the above, the configuration is simple, the frequency of the clock signal input to the microprocessor can be made variable, and the backup power supply can be used efficiently. The signal supply device comprises one oscillator for generating a signal of a constant frequency, and a plurality of clock signal generating means for generating a predetermined clock signal for each functional block of the microcomputer system based on the oscillation signal of the oscillator. .

[Industrial applications]

The present invention relates to a clock signal supply device for a microcomputer system, and more particularly to a clock signal supply device for a microcomputer system capable of supplying a clock pulse with a predetermined timing to each functional block of the microcomputer system.

[Conventional technology]

Generally, as shown in FIG.
In a microcomputer system 10 in which functional blocks such as a serial line controller 6 and a backup function 8 of a dynamic RAM 7 are connected by a bus 9, a clock signal which is the basis of the operation of each functional block is an oscillator 11 for each functional block. , 12, 13 are provided to obtain clock signals of respective required frequencies. Here, in FIG. 3, 14 is a refresh timing generation unit for dynamic RAM backup, 15 is a clock generator for driving the microprocessor 5, and 16 is a clock generator for the serial line control unit 6.

In this example, oscillators 11, 12, 13 are provided for each functional block.
And the clock generators 15 and 16 or the backup refresh timing generator 14 are provided to generate a clock signal having an optimum frequency for each functional block.

For example, the microprocessor 5 adopts a clock signal of high frequency, for example, 2 MHz in the normal case, and this frequency is variable by the software development tool.
Further, the serial line control unit 6 receives a clock signal of a frequency defined by the standard according to the information transmission speed to the line,
The refresh timing for the backup of the dynamic RAM 7 is set so that the oscillation frequency is selected so that the backup battery has the longest life.

[Problems to be Solved by the Invention]

By the way, in the above-described clock signal supply device of the microcomputer system, since the oscillator is provided corresponding to each functional block, there is a problem that the number of parts increases and the cost increases. In response to this, for example, as shown in FIG. 4, it is conceivable to supply the clock signal of each functional block from one clock generator 20 based on the signal from one oscillator 21. It is difficult to change the frequency of the clock signal supplied to the microprocessor by various methods, and when backing up the dynamic RAM, it is necessary to supply power for backup to even unnecessary parts for backup, and the power supply for backup There is a problem that it is not possible to use efficiently.

Therefore, the present invention provides a clock signal supply device for a microcomputer system, which has a simple structure and is capable of varying the frequency of a clock signal input to a microprocessor and efficiently using a backup power supply. The purpose is to do.

[Means for solving the problem]

Means for solving the above problems in the present invention,
It is composed of one oscillator 1 for generating a signal of a constant frequency and a plurality of clock signal generators 3 _{-1 to} 3 _-m for generating a predetermined clock signal based on the oscillation signal of the oscillator 1. A clock signal supply device of a microcomputer system 2 for generating a clock signal from a predetermined clock signal generator of the clock signal generators in a functional block including a dynamic RAM 24, wherein the clock signal is supplied to the microprocessor 29. A clock signal generator for generating a signal is a selecting means for selecting a signal from the oscillator 1 or a signal from an external oscillator, and a system clock generator 28 for generating a microprocessor clock signal based on the selected signal. And a clock signal for generating a clock signal in the dynamic RAM 24. The generator includes a backup refresh signal generator 22 that generates a backup refresh signal based on the signal from the oscillator 1, and a dynamic RAM based on the backup refresh signal or the microprocessor clock signal.
A clock for a microcomputer system which is provided with a selector 23 for selecting and generating a control clock signal, and in which the oscillator 1, the backup refresh timing signal generating means 22, the selector 23, and the dynamic RAM 24 can be operated by a backup power supply. It is a signal supply device.

[Action]

According to the present invention, the number of oscillators is one, and the structure is simple and the cost is not increased. Since the clock signal generator generates a clock signal that matches each functional block, it is sufficient to supply power only to the points directly related to this backup when backing up the dynamic RAM, so the backup power supply can be used efficiently. it can. Further, since the signal from the oscillator or the signal from the external oscillator can be selected and input by the selecting means, the clock signal of any frequency can be input to the microprocessor.

〔Example〕

An embodiment of a clock signal supply device for a microcomputer system according to the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the clock signal supply device of the microcomputer system according to the present invention.
In this embodiment, the clock signal supply device has a structure as shown in FIG. In the figure, 20 is a frequency of 15.9744M.
A crystal oscillator as an oscillator for transmitting a Hz signal, 21 is a clock driver, 22 is a backup refresh signal generator that generates a backup refresh timing signal, and 23 is the backup refresh signal described above when the main power supply fails, and A selector 24 selects and outputs a normal timing signal when the main power supply is used, and 24 represents a dynamic RAM. The backup power is supplied only to these functional blocks (enclosed by a chain line and indicated by reference numeral 25). In addition, in the figure
26 is a line control clock signal (614.4KH) which is obtained by dividing the signal of the crystal oscillator 20 by 1/26 into the serial line control unit 27.
z) control clock generator, further 28 is a microprocessor 29 and the above-mentioned crystal oscillator in the system.
A system clock generator that generates a system clock signal (1.9968MHz ≈ 2MHz) by dividing the signal from 20 into 1/8, 30 is a dynamic RAM from the system clock signal from the system clock generator 28 described above.
A dynamic RAM control signal generation unit 31 for generating a control timing signal, 31 indicates an external signal supply terminal for supplying an external signal of an arbitrary frequency to the system clock generator 28.

In such a clock signal supply device for a microcomputer system, during normal use of the main power supply, the crystal oscillator 20 is supplied with power from the main power supply and emits a signal. As a result, the line control clock generator 26 and the system clock generator 28 generate line control clock signals and system clock signals, respectively. Also, the dynamic RAM control timing signal generator 30
A timing signal for dynamic RAM control is issued from.

In this case, the selector 23
The RAM control timing signal is selected and the dynamic RAM is controlled by this signal.

When the software development tool is used in the state where the main power supply is used as described above, the system clock generator 31 is desired to drive the microprocessor 29 in the clock cycle according to the specifications of the software development tool to be used. An external signal of frequency can be input from the external input terminal 31.

Further, when the main power source is in a power failure state, only the above-mentioned portion to which the battery power source is supplied (indicated by the dashed line 25 in FIG. 3), that is, the crystal oscillator 20, the clock driver 21, the backup refresh Since the backup power is supplied to the timing generation unit 22, the selector 23 and the dynamic RAM 24, the backup refresh timing generation unit 22 outputs the backup refresh timing signal based on the signal from the crystal oscillator 20. It is preferable that the timing of this refresh timing signal is set so that the power consumption of the battery used is minimized. Further, the selector 23 selects the backup refresh timing signal and outputs it to the dynamic RAM 24.
Can execute refresh even in the event of power failure and can secure the stored programs and data. In addition, since the power of the backup battery is not supplied to locations unnecessary for refreshing the dynamic RAM, the backup battery can be used efficiently.

Therefore, according to the clock signal supply device of the microcomputer system according to the present embodiment, it is possible to prevent the cost increase because the crystal oscillator is one and the configuration is simple, and the microprocessor is provided with an arbitrary frequency. Since it is possible to input the external signal, the microprocessor can be driven at the clock timing according to the specifications of the program creation tool when the program creation tool is used. Further, according to the present embodiment, the timing of the refresh timing signal generated in the backup refresh timing generation section can be set so that the power consumption rate of the backup power can be minimized, and the portion not related to the refresh of the dynamic RAM can be performed. Since no power is supplied to the backup power source, the backup power source can be used efficiently.

〔The invention's effect〕

As described above, according to the present invention, the power supply for backup can be supplied by separating the portion of the clock supply device of the microcomputer system to be backed up, and the clock signal from the outside can be supplied to the microprocessor. Therefore, the configuration can be simplified, the cost can be prevented from rising, the power consumption of the backup system can be saved, and the clock signal of any frequency can be input to the microprocessor. This makes it easier to perform a clock margin test, and the microprocessor can be driven at the clock timing that matches the software development tool used, so that any software development tool can be used. Play.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram showing an embodiment of a clock signal supply device of a microcomputer system according to the present invention, and FIGS. 3 and 4 are blocks showing a conventional clock signal supply device. It is a figure. 1 ... Oscillator 2 ... Microcomputer system 2 _-1 to 2 _-n ... Functional block 3 _{-1 to} 3 _-m ... Clock signal generating means

Claims (1)

[Claims] 1. An oscillator (1) for generating a signal of a constant frequency, and a plurality of clock signal generators (3 _{-1 to} 3) for generating a predetermined clock signal based on the oscillation signal of the oscillator (1). _-m ) with a microprocessor (29) and dynamic RAM (24)
A clock signal supply device of a microcomputer system (2) for generating a clock signal from a predetermined clock signal generator of the clock signal generators in a functional block including: A clock signal generator for generating a clock signal selects a signal from the oscillator (1) or a signal from an external oscillator, and a microprocessor clock signal based on the selected signal. A clock signal generator including a system clock generator (28) for generating a clock signal for the dynamic RAM (24) is a backup refresh signal for generating a backup refresh signal based on a signal from the oscillator (1). Generator (22) and this backup refresh signal Or a selector (23) for selecting and generating a dynamic RAM control clock signal based on the microprocessor clock signal, the oscillator (1), the backup refresh timing signal generating means (22), and the selector (23). ),as well as,
A clock signal supply device for a microcomputer system in which the dynamic RAM (24) can be operated by a backup power supply.