JPS6198426A - Microcomputer containing clock frequency switching function - Google Patents

Abstract

PURPOSE:To minimize the power consumption of a microcomputer consisting of a CMOS by using a variable frequency divider which can set the frequency dividing number by an instruction given from a CPU and can switch the frequency with no spike produced even in an active mode. CONSTITUTION:A microcomputer 4 sends a large frequency dividing number to a variable frequency dividing circuit 2 through a data bus 5 in case the idle states including a waiting mode, etc. are rather frequent. Then the synchronization is secured for switching of frequency with no generation of a spike, etc. This reduces the power consumption. In case various states which should be processed at a time are produced, the computer 4 sends a small dividing number to the circuit 2. Thus the clock of the computer 4 is accelerated to complete the relevant processing within a prescribed period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microcomputer having a clock supply circuit.

[Conventional technology]

Conventionally, microcomputers used in mobile communications are
In addition to data transfer processing, it also executes various signal processing single-line control and wireless unit control. When determining the operating speed of a microcomputer, it was necessary to consider the case where these processes occur simultaneously, and to increase the operating frequency and number so that all of the processes would be completed within the specified time.

By the way, many mobile devices used in mobile communications are powered by batteries. Particularly in the case of portable devices, since each person always carries them, they must be lightweight and compact, and the restrictions required for batteries are even more severe. For this reason, the circuit used must have low power consumption, and CMO8
(complementary type MO8) is often used to configure a circuit. However, the CMO3 has the characteristic that power consumption increases in proportion to the input frequency, and in order to take advantage of the CMO3's feature of low power consumption, it is necessary to lower the operating frequency.

However, when using a microcomputer configured with CMO8, the operating frequency was increased in consideration of the possibility that various processes would occur simultaneously.

Although it was CMO8, it was not possible to reduce power consumption.

When using a mobile device, most of the time it is used is in standby mode, and the microcomputer only processes the transfer of received data and is mostly in idle mode, so the operating frequency is increased during standby mode. There's no need. Therefore, power consumption can be reduced by using a microcomputer with a methane pie function and controlling the device so that it enters a standby state when it is in an idle state.

[Problem that the invention seeks to solve]

However, if the standby state is frequently taken out to process the transfer of received data, the processing time before and after is so large that it cannot be ignored compared to the process of transferring the data, making it impossible to reduce power consumption. .

On the other hand, if the transfer processing of received data is performed using a FIFO (first in, first out) or DMA (direct memory access) controller and the standby state of the microcomputer is extended, the processing time before and after can be ignored. Although power consumption can be reduced, the circuit size increases, making it unsuitable for mobile devices that require miniaturization.

The object of the invention is to eliminate these drawbacks.

[Means for solving problems]

The present invention has a variable frequency divider circuit that allows the frequency division number to be set by a command from the CPU and can be switched without causing spikes even during operation. A microcomputer consisting of CMO8 is operated by a clock with a frequency of power consumption can be minimized.

[Principle and operation of the invention]

Figure 2 (a) shows a microcontroller with a standby function.
Figure 2(b) shows the relationship between the operating speed (operating speed is proportional to power consumption, so it can be considered as power consumption) and time when using a computer. This figure shows the relationship between operating speed and time when using a clock supply circuit or a microcomputer having a clock supply circuit. In the figure, the amount of work processed can be expressed as the product of operating speed and time, so 1
The diagonal lines in the figure indicate the amount of work processed. Also CMO8
Since the power consumption is proportional to the operating speed due to the nature of , the area of the diagonal line also represents the amount of power consumption. Figures 2(a) and 2(b) show the amount of work processed as shown in the same figure.
are the same, the area of the diagonal line is the area of Figure 2 (a) and Figure 2 (
b) is the same. However, in the case of Figure 2 (,), processing before and after standby is required, which increases the amount of work. Moreover, the amount of power consumption also increases accordingly. Therefore, the power consumption shown in FIG. 2(b) according to the present invention can be reduced accordingly.

In addition, since the present invention can be configured with a relatively simple variable frequency divider circuit, it requires a wake-up circuit (hereinafter referred to as WAKE UP circuit) for changing from standby state to operating state, and a FIFO or other circuit for maintaining standby state for a long time. DM
There is no need for a circuit together with the A controller, and transfer processing can always be performed at the optimum operating speed depending on the load of work at the time, and it can operate with the minimum necessary power consumption.

Although some types of microcomputers do not have a standby function, the present invention can be applied to all microcomputers.
Low/I by taking advantage of the characteristics of 8! It is possible to provide a small and lightweight mobile device with only one electricity cost.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail.

FIG. 1 shows an example of the configuration of the present invention. The variable frequency divider circuit 2 receives the designation of the frequency division number from the microcomputer 4 through the data bus 5, divides the clock 1, and inputs the divided clock from the clock output 3 to the clock input of the microcomputer 4. There is.

When the microcontroller 4 is in a relatively idle state such as during standby, the microcomputer 4 sends a large frequency division number to the variable frequency division circuit 2 through the data bus 5. The variable frequency divider circuit 2 switches to the frequency division number sent, but since the switching is done in synchronization, the
K doesn't cause jerking.

Switching is performed smoothly. Since the microcomputer 4 is configured with a CMO8 circuit, power consumption is reduced.

Next, when a situation that requires various simultaneous processing occurs, the microcomputer 4 sends a small frequency dividing number to the variable frequency dividing circuit 2, so the clock of the microcomputer 4 is not fast, and the predetermined time The process can be completed within a few days.

〔Effect of the invention〕

As explained above, by using the two aspects of the present invention, by changing the clock to the microcomputer with a relatively simple circuit, battery saving can be achieved in the same way as a microcomputer with a standby function. In addition, since there is no need for processing before and after standby, power consumption can be reduced accordingly, and WAKE! There is no need for circuits such as a UP circuit or an F/FO + DMA controller to maintain a standby state for a long time, and transfer processing can always be performed at the optimal operating speed depending on the workload at the time. It can operate with the minimum necessary power consumption.

Furthermore, it can be applied to microcomputers without a standby function, so CMO8! It is possible to provide a small and lightweight mobile device with low power consumption by taking advantage of its characteristics.

[Brief explanation of drawings]

FIG. 1(a) shows an example of the configuration of the present invention, and FIG. 2(a) shows the relationship between operating speed (power consumption) and time when a microcomputer with a standby function is used.
FIG. 2(b) shows the relationship between operating speed and time when a clock supply circuit to a CPU of the present invention or a microcomputer having a clock supply circuit is used. In fig. 1...Input clock, 2...Variable frequency divider circuit, 3...
・Around the minutes...Cout, 4...The circuit is composed of CMO8! Microcomputer, 5...data bus.

Claims (1)

[Claims] 1. It is characterized by having a variable frequency dividing circuit that can set a frequency dividing number by a command from the CPU and switching the frequency dividing number during operation, and a clock for operating the CPU is supplied from the variable frequency dividing circuit. microcomputer.