Merged Command Decoder for Half-Frequency Memory Timing
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Solution Overview
Problem
High-speed memory devices face challenges in capturing command address bits due to process voltage temperature (PVT) variations and three-dimensional stacked circuit structures, making it difficult to meet setup/hold timing requirements, especially in two-cycle commands like Write (WR) and Write Pattern (WRP) commands.
Innovation Solution
Implementing a merged command decoder that decodes common address bits shared between two or more commands, allowing these bits to be captured in a second cycle, with the remaining differentiating bit(s) used to distinguish between commands downstream, and utilizing half-frequency modes to reduce pipeline redundancy and expand the timing window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two-cycle commands are used to capture common address bits in the second cycle, then command functionality is improved, but timing window shrinks making capture difficult at higher speeds
Solution Approach 1:
The command address bits are segmented into two groups: common address bits (captured in first cycle) and remaining address bits (captured in second cycle). This segmentation allows the common bits to be decoded and used immediately, while the remaining bits are captured later, effectively extending the usable timing window for complex two-cycle commands.
Solution Approach 2:
The common address bits are captured and decoded in the first cycle before the remaining address bits are needed. This preliminary action of capturing common bits early allows the system to prepare decode signals in advance, reducing the timing pressure on the second cycle capture operation.
2Adaptability or versatility
If process voltage temperature variations and 3DS structures are present, then manufacturing flexibility is improved, but timing window shrinks further complicating capture
Solution Approach 1:
By segmenting the address bits into common and remaining portions, the system can tolerate larger timing variations caused by PVT and 3DS effects. The common bits are captured with relaxed timing requirements in the first cycle, while the remaining bits are captured in the second cycle, accommodating the reduced timing window.
Solution Approach 2:
The system dynamically adjusts the capture timing for different address bit groups based on the command type. For two-cycle commands, common bits are captured early with relaxed timing, while remaining bits are captured later, allowing the system to adapt to timing variations caused by manufacturing process differences.
3Measurement precision
If common address bits are captured in the second cycle, then command decoding is improved, but setup/hold timing requirements become difficult to meet
Solution Approach 1:
The address bits are segmented such that common bits are captured in the first cycle with relaxed timing requirements, enabling accurate decoding. The remaining bits are captured in the second cycle, ensuring that setup/hold timing requirements are met for the critical decode path while maintaining decoding accuracy.
Solution Approach 2:
The common address bits are captured and decoded in advance in the first cycle, performing the critical decoding operation before the remaining address bits are captured. This preliminary decoding action ensures that timing-critical operations complete with sufficient setup/hold time margins.
Data Source
AI summary
A memory device includes a command interface configured to receive a command from a host device via multiple command address bits. The memory device also includes a merged command decoder configured to receive the command and to determine whether the command matches a bit pattern corresponding to multiple command types. The merged command decoder is also configured to, in response to the command matching the bit pattern, asserting a latch signal. The memory device also includes a latch configured to capture the multiple command address bits based at least in part on assertion of the latch signal.