JPH01228006A - Clock signal supplying device for microcomputer system - Google Patents

Abstract

PURPOSE:To improve the power source efficiency for back-up by using one oscillator and plural clock signal generating means for respective function blocks. CONSTITUTION:A microcomputer system is equipped with a crystal oscillator 20, a clock driver 21, a refreshing signal generating part 22 for a back-up, a selector 23 and a dynamic RAM 24 and the electric power for back-up is supplied to these 25 only. The system has a serial line control part 27, a clock generator 26 for control, a microprocessor 29, a system clock generator 28 and a RAM control signal generating part 30. At the ordinary time of the use of a main power source, the selector 23 selects a RAM control timing signal and controls the RAM 24. Further, at the time of the main power source power failure, the electric power for back-up is supplied, the selector 23 selects a refresh timing signal for back-up and outputs it to the RAM 24. Thus, refreshing can be executed.

Description

Detailed Description of the Invention (Summary) This relates to a clock signal supply device for a microcomputer system, and in particular, a clock signal supply device for a microcomputer system that can supply a clock signal at a predetermined timing to each functional block of the microcomputer system. The purpose of this system is to have a simple configuration, to be able to vary the frequency of the clock signal input to the microprocessor, and to be able to use the backup power source efficiently. The signal supply device is composed of an oscillator that generates a signal of a constant frequency, and a plurality of clock signal generation means that generates a predetermined clock signal to each functional block of the microcomputer system based on the oscillation signal of the oscillator. .

(Industrial Application Field) The present invention relates to a clock signal supply device for a microcomputer system, and particularly to a clock signal supply device for a microcomputer system that can supply clock pulses at predetermined timing to each functional block of the microcomputer system. It is related to.

(Prior Art) Generally, as shown in FIG. 3, in a microcomputer system 10 in which functional blocks such as a microprocessor 5, a serial line control unit 6, and a backup function 8 of a dynamic RAM 7 are connected via a bus 9, each of these functions is Oscillators 11, 12, and 13 are provided for each functional block to obtain a clock signal having a required frequency for each functional block.

Here, in FIG. 3, 14 is a dynamic RAM backup glue fresh timing generator, 15 is a clock generator for driving the microprocessor 5, and 16 is a clock generator for driving the microprocessor 5.
indicates a clock generator for the serial line control section 6.

In this example, oscillators 11 and 12 are provided for each functional block.
．． 13 and a clock generator 15, 16 or a backup refresh timing generation section 14,
A clock signal with the optimum frequency is generated for each functional block.

For example, the microprocessor 5 uses a high frequency clock signal, for example, 2 MHz in normal cases, and this frequency is variable using a software development tool, and the serial line controller 6 uses a clock signal for transmitting information to the line. A clock signal with a frequency specified by the standard depending on the speed,
Further, the refresh timing for backup of the dynamic RAM 7 is such that the oscillation frequency is selected so that the backup battery lasts the longest.

[Problem to be solved by the invention]

However, in the above-described clock signal supply device for a microcomputer system, since an oscillator is provided corresponding to each functional block, there is a problem that the number of parts increases and the cost increases. Correspondingly, it is conceivable to supply clock signals for each functional block from one clock generator 20 based on signals from - oscillators 21, as shown in FIG. 4, for example.
With this method, it is difficult to vary the frequency of the clock signal supplied to the microprocessor, and when backing up dynamic RAM, backup power must be supplied even to parts that are not needed for backup. There is a problem in that the power source cannot be used efficiently.

SUMMARY OF THE INVENTION Therefore, the present invention provides a clock signal supply device for a microcomputer system that has a simple configuration, can vary the frequency of a clock signal input to a microprocessor, and can efficiently use a backup power source. The purpose is to

(Means for Solving the Problems) Means for solving the above problems in the present invention are as shown in FIG. 1, as shown in FIG. 1, and each functional block 2-1 to 2 of the microcomputer system 2 based on the oscillation signal of the oscillator 1.
3-n to 3-1.

(Function) According to the present invention, there is only one oscillator, the structure is simple, and the cost does not increase. Since the clock signal generation means generates a clock signal that matches each functional block, when backing up the Dynamitsu RAM, it is sufficient to supply power only to the parts directly related to this backup, so the backup power source can be used efficiently. can.

(Embodiment) Hereinafter, an embodiment of a clock signal supply device for a microcomputer system according to the present invention will be described based on the drawings.

FIG. 2 shows an embodiment of a clock signal supply device for a microcomputer system according to the present invention. In this embodiment, the cross signal supply device has a configuration as shown in FIG. In the same figure, 20 is the frequency 15.97
A crystal oscillator as an oscillator that emits a 44 MHz signal; 21 is a clock driver; 22 is a backup refresh signal generation unit that generates a backup refresh timing signal; Further, a selector 24 which selects and outputs a normal timing signal when the main power source is used indicates a dynamic RAM. and these functional blocks (indicated by the dot-dashed line and the enclosing code 25)
Backup power is supplied only to the

Further, in the figure, 26 is a control clock generator that divides the signal of the crystal oscillator 20 by 1/26 to generate a line control clock signal (614, 4KH2) for the serial line control unit 27, and 28 is a The microprocessor 29 and the system receive a system clock signal (1,99
A system clock generator 30 generates a dynamic RAM control timing signal from the system clock signal from the system clock generator 28 described above.
The AM control signal generation section 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 operation when the main power supply is used, the crystal oscillator 20 is supplied with power from the main power supply and generates a signal. As a result, the line control clock generator 26 and the system clock generator 28 generate a line control clock signal and a system clock signal, respectively. Further, the dynamic RAM control timing signal generation section 30 generates a timing signal for dynamic RAM control.

In this case, the selector 23 selects this dynamic RAM control timing signal to control the dynamic RAM control timing signal.
M is controlled by this signal.

When using a software development tool while using the main power supply in this way, the system clock generator 31 is required to have a desired frequency to drive the microprocessor 29 at a clock cycle that matches the specifications of the software development tool being used. External signals can be input from the external input terminal 31.

In addition, when the main power supply is in a power outage state, only the parts to which the battery power is supplied as described above (indicated by a dot-and-dashed line and the enclosing code 25 in FIG. 3), that is, the crystal oscillator 20, the clock driver 21, the backup Refresh timing generator 22, selector 23 and dynamic RAM
Since backup power is supplied to the crystal oscillator 24, the backup refresh timing generation section 22 outputs a 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. Furthermore, since the selector 23 mentioned above selects this backup refresh timing signal and outputs it to the dynamic RAM 24, the dynamic RAM 24 can be refreshed even in the event of a power outage, and the stored programs and data can be secured. Can be done. Further, since the power of the backup battery is not supplied to areas unnecessary for refreshing the dynamic RAM, the backup battery can be used efficiently.

Therefore, according to the clock signal supply device for a microcomputer system according to the present embodiment, since the configuration is simplified by using only one crystal oscillator, it is possible to prevent an increase in cost, and also it is possible to prevent an increase in cost by using a single crystal oscillator. Since external signals can be input, when using a programming tool, the microprocessor can be driven at a clock timing that matches the specifications of the programming tool. Further, according to the present embodiment, the timing of the refresh timing signal generated in the backup refresh timing generation section can be set such that the consumption rate of backup power is minimized, and the portions of the dynamic RAM not related to refresh can be adjusted to minimize the consumption rate of backup power. Since power is not supplied to the main unit, the backup power source can be used efficiently.

(Effects of the Invention) As explained above, according to the present invention, the clock supply device of a microcomputer system includes an oscillator that generates a signal of a constant frequency, and an oscillation signal of the oscillator that generates a clock supply device for a microcomputer system. Since each functional block is configured with a plurality of clock signal generation means that generate a predetermined clock signal, the configuration can be simplified, and an increase in cost can be prevented, and the backup system can be In addition to reducing power consumption, it also becomes possible to input a clock signal of any frequency to the microprocessor, making it easier to perform clock margin tests. It has the advantage that it can drive a processor and can be used with any software development tool.

[Brief explanation of the drawing]

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 for a microcomputer system according to the present invention, and FIGS. 3 and 4 are block diagrams showing a conventional clock signal supply device. It is a diagram. 1... Oscillator 2... Microcomputer system 2-1 to 2-o
...Function block

Claims (1)

[Claims] An oscillator (1) that generates a signal with a constant frequency, and each functional block (2_-_1) of a microcomputer system (2) based on the oscillation signal of this oscillator (1).
A plurality of clock signal generating means (3_-_1) to (3_-_m) that generate predetermined clock signals at ~(2_-_n)
) A clock signal supply device for a microcomputer system.