Clock Gating After Reset to Prevent Timing Violations
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Solution Overview
Problem
In high-performance digital chips with integrated circuit modules, asynchronous reset signals often fail to be accurately captured, leading to timing violations and instability during post-design operations, requiring complex synchronization methods to prevent failures.
Innovation Solution
A clock management unit comprising flip-flops and a clock gate is used to maintain a predetermined interval between the release of a reset signal and the provision of a clock signal to an external circuit, ensuring no clock edge transitions occur for at least two periods after reset activation, thereby preventing timing violations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reset signal is supplied to an external circuit during clock signal operation, then the external circuit can be reset, but timing violations occur when clock edges coincide with reset signal transitions
Solution Approach 1:
The patent applies preliminary action by delaying the reset signal through a chain of flip-flops before it reaches the external circuit. The reset signal is delayed for at least two clock periods through sequential flip-flop stages, ensuring that reset transitions occur well before any subsequent clock edges, thereby preventing timing violations before they can happen.
Solution Approach 2:
The patent uses flip-flops as intermediary elements between the reset signal source and the external circuit. These flip-flops act as mediators that buffer and delay the reset signal, creating a temporal separation between reset transitions and clock edges, thus preventing direct interference between the two signals.
2Measurement precision
If post-static timing analysis is performed for each module to ensure sufficient interval between reset release and clock rising edge, then timing violations can be detected, but the testing process becomes complex and time-consuming
Solution Approach 1:
The patent performs preliminary timing protection by structurally ensuring a minimum two-clock-period interval between reset release and subsequent clock edges through the flip-flop delay chain. This preliminary action embeds timing safety directly into the circuit architecture, eliminating the need for extensive post-design timing analysis and significantly reducing testing time.
Solution Approach 2:
The circuit performs self-service by automatically maintaining the required timing interval through its internal flip-flop structure. The delay mechanism is self-regulating and does not require external verification or complex testing procedures, as the circuit inherently guarantees timing compliance through its design.
3Productivity
If the clock signal is continuously supplied to the external circuit, then the circuit operates continuously, but power consumption increases when reset is active
Solution Approach 1:
The patent applies periodic action by controlling the clock signal to the external circuit in a periodic manner - the clock is enabled only after the reset signal has been active for at least two full clock periods. This periodic enabling/disabling of the clock signal ensures the external circuit operates only when timing conditions are satisfied, reducing unnecessary power consumption during reset transitions.
Solution Approach 2:
The patent uses feedback by monitoring the reset signal state and using it to control the clock gate that supplies the clock signal to the external circuit. The clock signal is gated based on the delayed reset signal feedback, ensuring the clock is suppressed during the critical reset period and only enabled after the timing interval has elapsed, thereby reducing power consumption during reset operations.
Data Source
AI summary
A clock management unit includes a delay unit; and an output unit, wherein the delay unit receives a clock signal and a reset signal for resetting an external circuit, and supplies a delayed reset signal to the output unit, wherein the output unit supplies to the external circuit an external clock signal obtained by processing the clock signal and the delayed reset signal, and wherein the external clock signal does not experience any edge transitions during at least two periods of the clock signal after the reset signal transitions to an active state for resetting the external circuit.