Memory Controller Suspend Handshake for DRAM Self-Refresh
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Solution Overview
Problem
Existing programmable integrated circuit devices (ICs) face data loss issues when entering a low power suspend mode, as subsystems are shut down, affecting external memory devices.
Innovation Solution
A memory controller block within the programmable IC is configured to initiate a self-refresh mode in the memory device before shutting down, ensuring data preservation during suspend mode by generating a suspend acknowledgement signal, allowing the IC to enter suspend mode without data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the programmable IC is placed into low power suspend mode by shutting down subsystems, then power consumption is reduced, but data loss occurs in the external memory device
Solution Approach 1:
The memory controller initiates a self-refresh mode in the external memory device before the programmable IC enters suspend mode. This preliminary action ensures that data is preserved in the memory device during the transition to low power mode, preventing data loss while enabling power savings. The self-refresh mode is maintained throughout the suspend period, and the memory controller remains in a low power state.
2Loss of energy
If the memory controller shuts down subsystems to enter suspend mode, then power consumption decreases, but the memory device cannot maintain data integrity
Solution Approach 1:
Before entering suspend mode, the memory controller proactively places the memory device into self-refresh mode, ensuring data integrity is maintained before the shutdown sequence begins. This preliminary configuration allows the system to transition to low power mode without compromising data reliability.
Solution Approach 2:
The self-refresh mode acts as an intermediary state between active operation and complete shutdown. The memory device enters this intermediate state where it maintains data integrity through periodic refresh cycles while consuming minimal power, serving as a bridge that preserves reliability during the transition to suspend mode.
3Use of energy by stationary object
If subsystems are shut down for suspend mode operation, then energy consumption is reduced, but data preservation in external memory becomes problematic
Solution Approach 1:
The system performs a preliminary action by initiating self-refresh mode in the external memory device before the suspend mode takes effect. This ensures data preservation is established in advance, allowing the memory controller to subsequently enter low power state without risking data loss.
Solution Approach 2:
The memory device serves itself by entering self-refresh mode, where it autonomously maintains its data through periodic refresh operations without requiring active control from the memory controller. This self-service capability allows data preservation while the controller remains in a low power state.
Data Source
AI summary
A programmable integrated circuit device (IC) can include a configuration controller configured to assert a suspend request signal responsive to an input triggering suspend mode within the programmable IC and a memory controller block coupled to the configuration controller and a memory device. The memory controller block can be configured to place the memory device in self refresh mode in response to the suspend request signal and assert a suspend acknowledgement signal subsequent to placing the memory device in self refresh mode. The configuration controller can continue implementing suspend mode within the programmable IC in response to assertion of the suspend acknowledgement signal.