USB Controller Power Management During Data Transmission
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Solution Overview
Problem
The frequent transmission and reception of periodic pattern data during the recovery of USB3.0 from low-power states to a fully operational state can cause Electro Magnetic Interference (EMI) during printing or scanning, posing a risk to data communication.
Innovation Solution
An information processing apparatus with a USB controller that receives a transmission instruction, shifts to a low-power state during data transmission, and prohibits shifting to low-power states during data transmission from the apparatus to an external device, thereby avoiding the execution of the training sequence and subsequent EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the USB controller shifts to low-power states during data transmission, then power consumption is reduced, but EMI risk increases due to frequent training sequence execution
Solution Approach 1:
The system proactively prevents EMI by checking whether data transmission is ongoing before allowing transition to low-power states. The prohibition unit blocks transitions during active transmission, eliminating the root cause of EMI before it can occur. This anticipatory control resolves the contradiction by sacrificing some power-saving opportunities to prevent harmful EMI effects.
2Loss of energy
If the USB controller frequently transitions between low-power and operational states, then power-saving effect is improved, but communication stability deteriorates due to EMI
Solution Approach 1:
The system continuously monitors the state of data transmission through the reception unit and uses this feedback to control transitions to low-power states. When transmission is detected, the prohibition unit activates to prevent transitions; when idle, transitions are permitted. This feedback mechanism dynamically balances power-saving needs with communication stability, resolving the contradiction adaptively.
3Adaptability or versatility
If the training sequence is executed frequently for state recovery, then power management flexibility is improved, but EMI interference increases
Solution Approach 1:
The system dynamically adjusts its power management behavior based on real-time transmission conditions. Rather than rigidly enforcing power-saving transitions or completely avoiding them, the system adapts its transition timing to match the actual data transmission state. This dynamic control maintains power management flexibility while preventing EMI-generating transitions during critical transmission periods.
Data Source
AI summary
According to one embodiment, an information processing apparatus includes a universal serial bus (USB) controller capable of shifting to a low-power state and configured to transmit data with a predetermined pattern to a personal computer (PC) when the USB controller is recovered from the low-power state. The information processing apparatus includes a hardware logic configured to cause the USB controller to shift to the low-power state, a reading unit configured to read an image formed on a document according to a reading instruction, and a physical layer (PHY) configured to transmit, to the PC, image data on the document with the image read by the reading unit. The information processing apparatus prohibits the USB controller from shifting to the low-power state during a period in which the PHY transmits the image data to the PC.