Clock Switching Circuit Prevents Hazards via Dual Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional clock switching circuits malfunction due to unwanted pulses and duty ratio distortion when switching between unsynchronized clocks of different frequencies, leading to metastable states in circuits like flip-flops.
Innovation Solution
A clock switching circuit with first and second synchronization circuits to synchronize the clock selection signal with each clock, and a clock selection circuit that outputs high or low levels in synchronization with the selected clock, using a series of flip-flops to prevent hazards and distortions by ensuring stable clock switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional clock switching circuit switches between clocks simply in response to a clock selection signal, then the switching operation is simple and fast, but unwanted pulses and duty ratio distortion occur when clocks are not synchronized
Solution Approach 1:
The first synchronization circuit synchronizes the clock selection signal with the first clock before the switching operation. This preliminary synchronization ensures that the selection signal and clock are aligned, preventing unwanted pulses and duty ratio distortion during the subsequent switching between unsynchronized clocks of different frequencies.
Solution Approach 2:
The second synchronization circuit acts as an intermediary between the already-synchronized clock selection signal and the second clock. It synchronizes the selection signal with the second clock, ensuring proper timing alignment and preventing signal integrity issues during the clock switching operation.
2Reliability
If synchronization circuits are added to prevent hazards, then clock switching becomes reliable, but the device complexity increases
Solution Approach 1:
The synchronization function is divided into two separate synchronization circuits: the first synchronization circuit handles synchronization with the first clock, and the second synchronization circuit handles synchronization with the second clock. This segmentation allows each circuit to be optimized for its specific clock frequency, improving reliability while keeping individual circuit modules relatively simple.
Data Source
AI summary
This invention provides a clock switching circuit that can switch clocks without causing a hazard or a distortion of a duty ratio of the clocks. The clock switching circuit of this invention includes a first synchronization circuit that synchronizes a clock selection signal with a first clock, a second synchronization circuit that synchronizes with a second clock the clock selection signal that has been synchronized with the first clock by the first synchronization circuit and a clock selection circuit that outputs “1”, that is a high level, in synchronization with the clock selection signal that has been synchronized with the first clock by the first synchronization circuit and after that selects the second clock in synchronization with the clock selection signal that has been synchronized with the second clock by the second synchronization circuit.