Image Signal Processor Stall Counting Circuit
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Solution Overview
Problem
Image signal processors face challenges in quickly processing large image signals, leading to potential overflow and frame drop issues, which can result in excessive power consumption due to low discriminative ability of stall counting values.
Innovation Solution
An image signal processor is designed with a stall counter that generates a highly discriminative stall counting value by using a throttle buffer, a module for image calculation, a splitter for signal distribution, and buffer checking and throughput checking circuits to enable accurate stall counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the image signal processor continues to receive image signals from the image sensor, then the processing throughput is maintained, but overflow may occur causing frame drop
Solution Approach 1:
The patent implements preliminary action by checking buffer usage capacity before overflow occurs. The buffer checking circuit monitors the usage capacity of the first throttle buffer and generates a stall counting enable signal in advance when the usage capacity exceeds a threshold, allowing the system to take preventive measures before overflow happens.
Solution Approach 2:
The patent employs feedback mechanisms where the buffer checking circuit continuously monitors buffer status and provides feedback signals. When the usage capacity exceeds the threshold, the circuit generates a stall counting enable signal that feeds back to control the stall counting circuit, creating a closed-loop control system that dynamically adjusts processing based on buffer status.
2Measurement precision
If the stall counter counts stall signals continuously, then overflow detection capability is maintained, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the stall counting operation conditional rather than continuous. The stall counting circuit is enabled only when the buffer checking circuit detects that usage capacity exceeds the threshold, and disabled otherwise. This dynamic enabling/disabling mechanism adjusts the counting operation based on real-time buffer status, maintaining accuracy when needed while reducing power consumption during normal operation.
Solution Approach 2:
The patent changes the operational parameter of the stall counter from continuous counting to conditional counting based on buffer usage threshold. By using the stall counting enable signal to control the counting operation, the system transitions between different operational states (counting vs. non-counting) based on buffer status, optimizing the balance between detection accuracy and power consumption.
3Reliability
If the stall counting value is generated with high discriminative ability, then overflow detection reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the overflow detection function into multiple specialized circuits: a buffer checking circuit for monitoring usage capacity, a threshold comparison mechanism, and a stall counting circuit for actual counting. This segmentation allows each component to perform its specific function efficiently, improving overall detection reliability while keeping individual components relatively simple.
Solution Approach 2:
The patent introduces an intermediary stall counting enable signal that mediates between the buffer checking circuit and the stall counting circuit. This intermediary signal acts as a control gate, enabling the counting circuit only when buffer usage exceeds the threshold, thereby improving detection reliability without requiring the counting circuit to operate continuously or handle all cases.
Data Source
AI summary
An image signal processor comprising a throttle buffer configured to receive image signals, and buffer and output the image signals; a module configured to receive the buffered image signals, perform calculations on the buffered image signals, and output calculated image signals; a splitter configured to receive the calculated image signals and send a portion of the received calculated image signal to a path; a buffer checking circuit configured output a stall counting enable signal at a logic high, in response to a ratio of a current usage capacity to a total capacity of the throttle buffer being greater than a ratio of a capacity of one line of the portion to the total capacity of the throttle buffer, based on a received memory status signal; and a stall counting circuit configured to count a stall signal input from the path, in response to receiving the stall counting enable signal.