Boundary Scan Receiver with Shared Comparator Reference Switching

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Solution Overview

Problem

Conventional boundary scan receivers require multiple comparators for differential signaling, increasing circuit complexity and area, especially when switching between AC and DC modes, due to the need for separate reference levels and hysteresis delays.

Innovation Solution

A single shared comparator is used with reference selection logic to control the comparator's reference levels, allowing it to detect inputs above, below, or between thresholds in both AC and DC modes, and a high-pass filter simplifies the comparator design by maintaining one input at a constant value, reducing complexity and area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple comparators are used for differential signaling in boundary scan receivers, then detection accuracy is improved, but circuit area and complexity increase

Engineering Contradiction:

Improvedetection accuracyVSAvoidcircuit area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent combines multiple comparator functions into a single shared comparator that can be time-multiplexed to perform differential signaling detection. The comparator is shared between AC and DC modes, and also shared between differential and single-ended modes, eliminating the need for separate comparators for each function while maintaining detection accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single comparator is designed to be universal, capable of performing multiple functions including AC mode detection, DC mode detection, differential signaling detection, and single-ended signaling detection. This multi-functionality is achieved through time-multiplexing and mode-select logic that configures the comparator for different operating conditions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If separate reference levels are used for AC and DC modes, then mode-specific detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvemode-specific detection accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The reference level is made dynamic rather than static, allowing it to be switched between different values based on the operating mode. A mode-select mechanism dynamically configures the reference level to appropriate values for AC or DC mode, enabling the single comparator to achieve mode-specific detection accuracy without requiring separate hardware for each mode.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The reference level parameter is changed based on the operating mode. The system selectively applies different reference level values to the comparator depending on whether AC or DC mode is active, allowing the same hardware to adapt its detection characteristics to match the requirements of different signaling modes.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If hysteresis delay is implemented in comparators, then signal detection stability is improved, but propagation delay increases

Engineering Contradiction:

Improvesignal detection stabilityVSAvoidpropagation delay

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The system uses periodic sampling and time-multiplexed operation where the single comparator is activated in periodic intervals to perform both AC and DC mode detections. This periodic action allows hysteresis to be applied selectively during detection windows while maintaining overall system responsiveness, balancing stability requirements with timing constraints.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces the receiver circuit area and simplifies design by enabling efficient switching between AC and DC modes with a single comparator, improving detection accuracy and stability while minimizing propagation delays and oscillations.

Implementation Method 1

a high-pass filter simplifies the comparator design by maintaining one input at a constant value

Methodology Applied

Scientific EffectHigh-pass filtering: Filter (electronic)

Implementation Method 2

the comparator is controllable to detect whether the input is above an upper threshold, below a lower threshold, or in between

Methodology Applied

Scientific EffectVoltage comparison:

Implementation Method 3

AC detection involves comparing the output against two thresholds (a positive threshold and a negative threshold) to identify when the output crosses either threshold

Methodology Applied

Scientific EffectEdge detection:

Data Source

PatentUS9964593B1Boundary scan receiver

Publication Date: 2018.05.08 CADENCE DESIGN SYST INC

AI summary

A system, method, and circuits for processing a boundary scan result involve receiving the boundary scan result as input data to a comparator, and performing a comparison based on the input data and a selected reference level to form a comparison result. A capture device that stores the comparison result is set, reset or write enabled based on the comparison result and a reference value indicating which of two reference levels is the selected reference level. Additionally, a determination is made whether to change the selected reference level for a subsequent comparison based on the comparison result, the reference value, and the output of the capture device.