Scannable Storage Circuit Timing for Lower Set-Up Delay
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The additional delay introduced by scan flip-flops in synchronous circuits due to added testing circuitry reduces the maximum operating frequency and increases the set-up time, limiting the performance of the circuit.
Innovation Solution
A method and system for control signal synchronization in scannable storage circuits, where each storage circuit includes a scan enable signal, an input transmission gate, and a loop transmission gate that synchronously closes a hold loop when the input transmission gate is opened, reducing set-up time and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If scan flip-flops are used to enable testing functionality, then testing capability is improved, but propagation delay increases and maximum operating frequency decreases
Solution Approach 1:
The patent implements dynamic control of transmission gates based on the scan enable signal state. When in functional mode, the hold loop transmission gate remains closed to provide a direct path. When in scan mode, the transmission gate opens to allow scan data input. This dynamic switching optimizes performance for each operational mode separately.
Solution Approach 2:
The patent segments the data path into two separate physical paths: one for functional data input and another for scan data input. Each path has its own optimized transmission gate control, allowing independent optimization of each path's performance characteristics without compromising the other.
2Adaptability or versatility
If scan flip-flops with additional testing circuitry are used, then testing capability is improved, but set-up time increases
Solution Approach 1:
The patent prepares the hold loop transmission gate control signal in advance by synchronizing it with the input transmission gate opening. This preliminary action ensures that when the input transmission gate opens to accept new data, the hold loop transmission gate is already in the correct state to receive and hold the data without additional delay.
Solution Approach 2:
The patent introduces a synchronized control signal as an intermediary that coordinates the opening of the input transmission gate with the state of the hold loop transmission gate. This intermediary signal ensures proper timing alignment between the two gates, preventing setup time violations.
3Adaptability or versatility
If additional circuitry for scan enable signal is added, then testing capability is improved, but power consumption increases
Solution Approach 1:
The patent uses periodic clock signals to control the transmission gates, enabling them only during the appropriate phases of the clock cycle. This periodic activation reduces power consumption compared to continuously enabled gates, as the gates remain in high-impedance state during inactive periods.
Solution Approach 2:
The patent discards the use of the hold loop transmission gate during functional operation by keeping it closed, and recovers its use during scan operation by opening it. This selective usage pattern ensures that the additional circuitry consumes minimal power during normal operation while being fully functional during testing.
Data Source
AI summary
A system of control signal synchronization of a scannable storage circuit includes any number of storage circuits interconnected together with logic circuitry to form at least a portion of a functional circuit. Each of the storage circuits may include an input transmission gate to apply any one of a data input and a scan input to a storage element of the storage circuit based on an input circuitry that considers the state of the scan enable signal and a timing signal of a clock associated with the storage element. In addition, a control signal in a master latch of the storage element may synchronously close a hold loop in the master latch when the input transmission gate is opened upon the timing signal of the clock transitioning to a different state.