Latch Circuit Timing Decoupling for Diverse Data Sources
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Solution Overview
Problem
Circuit blocks that require a valid data signal for the entire duration of a control signal assertion face challenges when data sources have different timing capabilities, making it difficult for some sources to provide the data signal consistently.
Innovation Solution
A latch circuit design that captures and holds input signal values independently of the falling edge of the control signal, allowing multiple data sources with different timing to provide valid data, ensuring the circuit operates correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the data signal is required to be valid for the entire duration of the control signal assertion, then the circuit block can work properly, but data sources with different timing capabilities cannot provide the data signal consistently
Solution Approach 1:
The latch circuit captures the data signal at a specific moment (on the rising edge of the control signal) before the control signal assertion completes, storing it in a stable state. This preliminary capture action allows the data to be held valid for the entire control signal duration even though the data source only needs to provide it briefly, resolving the timing compatibility issue between diverse data sources and the circuit block requirements
2Reliability
If the data signal must be provided for the entire control signal assertion duration, then proper circuit operation is ensured, but the setup time requirement becomes more stringent
Solution Approach 1:
The latch circuit performs preliminary capture of the data signal at the rising edge of the control signal, establishing the data validity requirement only at that moment rather than for the entire control signal duration. This reduces the setup time window from the full control signal assertion period to just the brief window around the rising edge, making timing requirements more manageable
3Adaptability or versatility
If data sources use different clocks to clock their circuitry, then design flexibility is improved, but the ability to provide data for the entire control signal assertion becomes difficult or impossible
Solution Approach 1:
The latch circuit captures data from sources with different clock timings at its own rising edge moment, storing the data in a stable state that persists for the entire control signal assertion. This preliminary capture at a single moment allows data sources to operate independently on different clocks, as they only need to ensure data is stable briefly around the latch's rising edge rather than maintaining it throughout the entire control signal duration
Solution Approach 2:
The latch circuit acts as an intermediary between diverse data sources with different timing and the circuit block requiring stable data. It buffers and holds the data signal, decoupling the timing requirements of the data source from the control signal assertion duration, thereby enabling compatibility between differently clocked components
Data Source
AI summary
Circuitry for latching receives an input signal and a control signal and provides an output signal. In one embodiment, the setup time (t(SL) and t(SH)) of the input signal with reference to the control signal is to the first edge of the control signal, the holding time (t(HL) and t(HH)) of the input signal with reference to the control signal is independent of the second edge of the control signal, and the output signal goes to a predetermined state in response to the second edge of the control signal. In one embodiment, the control signal may be a clock. The circuitry for latching may be used with static circuits and/or with dynamic circuits.