SAS Backplane Presence Detection Using Resistor Divider Voltage Levels
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Solution Overview
Problem
Existing storage backplanes face challenges in determining the presence and activity of mass storage devices using SAS internal connectors, as there is no dedicated pin for conveying presence information, and existing solutions require complex circuits to drive LEDs, occupying valuable board space.
Innovation Solution
A resistor divider circuit is used to generate voltages indicating the mated status and activity of mass storage devices, utilizing a single pin per device, connected to the SAS receptacle connector, allowing the enclosure management integrated circuit to determine presence and activity, and drive LEDs accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated pin is added to SAS internal connectors to convey presence information, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing READY LED pin serve multiple functions: it still indicates drive activity status, and additionally conveys presence information through voltage level differentiation. By making this single pin universal for both activity indication and presence detection, the patent avoids adding dedicated pins while achieving accurate presence detection.
Solution Approach 2:
The patent changes the voltage parameter of the READY LED pin to encode presence information. When a device is present, the pin maintains a specific voltage range; when absent, the voltage differs. This parameter change allows a single pin to convey presence status without adding physical connector pins.
2Ease of operation
If an open collector or open drain transmitter circuit is used to drive LED from the READY LED pin, then LED driving capability is improved, but board space increases
Solution Approach 1:
The patent enables the READY LED pin to directly drive the LED without requiring additional open collector or open drain transmitter circuits. The pin's existing pull-up resistor and voltage levels are sufficient to directly control LED on/off states, making the system self-sufficient and eliminating the need for extra driver circuitry that would consume board space.
3Loss of information
If multiple pins are used to convey presence and activity information, then information completeness is improved, but device complexity increases
Solution Approach 1:
The patent merges the presence indication function with the existing READY LED pin activity indication function. By combining both information streams into a single pin's voltage levels, the patent reduces circuit complexity while maintaining complete information conveyance about both presence and activity states.
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
Enables efficient detection of mass storage device presence and activity using existing SAS connectors without additional pins, reducing board space requirements and simplifying the circuitry needed for status indication.
Implementation Method 1
a resistor divider circuit is disclosed that is operative to generate a voltage indicating whether a mass storage device has been mated to a mass storage backplane and whether the mass storage device is active
Data Source
AI summary
Technologies are described herein for detecting the presence and activity of a mass storage device. A resistor divider circuit generates a voltage indicating whether a mass storage device has been mated to a mass storage backplane and whether the device is active. The circuit provides a voltage within a first range when the device is not mated to the storage backplane, and provides a voltage within a second range when the device is mated to the storage backplane but is inactive. The circuit also provides a voltage within a third range when the device is mated to the storage backplane and is active. The circuit can be connected to an integrated circuit that can determine, based on the output of the resistor divider circuit, whether the device has been mated to the storage backplane and whether the device is active.