JPH0250715A - Clock controller - Google Patents

Abstract

PURPOSE:To flexibly switch a clock source through software control by providing a clock controller with a means for interpreting a software instruction, a means for holding the selecting state of the clock source and a means for making a clock source selecting state effective. CONSTITUTION:Which system clock source is to be used is set up by a software switch 32. A system clock source 21 when the set value is '0' or a system clock source 22 in the case of '1' is selected by a clock source switching selector 35. Then a switch control switching selector 34 is switched by setting up a software switch 33. The selector 34 connects a software switch 10 to the selector 35 when the switch is '0' or connects the switch 32 in case of '1'. Thus, the clock sources can be switched through software control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a clock control device in an information processing system having two or more different clock sources.

[Conventional technology]

Conventional clock control devices are capable of synchronizing information processing systems that operate with multiple independent locks (see Figure 2 (a)) and switching to another clock source in the event of a clock failure (second clock source).
(see Figure (b)), etc., and is composed of hardware switches that are completely independent of the information processing system.

Synchronization of a plurality of information processing systems refers to operating each information processing system, which normally operates independently, with the same clock in order to operate at high speed as one system. In FIG. 2(a), the normal information processing system A
, B are set to have separate clock sources in order to operate independently, and the hardware switches are set to supply the same clock source to both systems only when they are operated in synchronization. Set the switch.

When a clock failure occurs, the system is operated by switching to a clock source that does not have the failure (FIG. 2(b)).

[Problem to be solved by the invention]

In the conventional clock control device described above, the clock source can only be switched using a hardware switch, so it is possible to synchronize multiple information processing systems using software control, or switch to another clock source in the event of a clock failure. The disadvantage is that automatic switching is not possible.

[Means to solve the problem]

The clock control device of the present invention, in an information processing system having two or more different clock sources, includes means for interpreting a software instruction, means for maintaining a selection state of the clock source, and a means for maintaining a selection state of the clock source. and means for enabling the clock source, and the clock source is configured to be switched by software control.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 10 is a switch for switching the clock source, 21 and 22 are system clock sources, 30 is a clock control device, and 40 is an information processing system operated by the system clock. The clock control device 30 also includes a software instruction decoder 31 for interpreting software instructions, a control F/F software switch 32 for selecting a clock source, and a control F/F software switch 33 for enabling the software switch 32.
, a switch control switching selector 34 that switches the system clock source switching signal between a hardware switch and a software switch, and a clock source switching selector 35.

For clock control by software, first, the software switch 32 is used to set which system clock source is to be used. If the set value is "0", the system clock source 21 is selected as the clock source, and if it is "1", the system clock source 22 is selected as the clock source by the clock source switching selector 35. Then, by setting the software switch 33, the switch control is performed. The switching selector 34 is switched.The switch control switching selector 34 is the software switch 33.
If it is "0", the hardware switch 10 is connected to the clock source switching selector 35, and if it is "1", the software switch 32 is connected to the clock source switching selector 35.

The absence of the hardware switch 10 does not deviate from the purpose of the present invention, which is soft switching. The role of the hardware switch 10 in this embodiment is to set default values at system startup.

〔Effect of the invention〕

As explained above, the present invention has means for interpreting software instructions, means for holding the selected state of the clock source, and means for validating the selected state of the clock source. It has the effect of being flexible through control.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a clock control device according to the present invention, and FIGS. 2(a) and 2(b) are block diagrams showing a conventional example. 10... Hardware switch, 21.22... System clock source, 30... Clock control device,
31...Software instruction decoder, 32.33...
- Software switch, 34...Selector for switch control switching, 35...Selector for clock source switching.

Claims (1)

[Claims] An information processing system having two or more different clock sources includes means for interpreting software instructions, means for maintaining a selected state of the clock source, and means for validating the selected state of the clock source. A clock control device characterized in that the clock source can be switched by software control.