Chip Select Control Circuit for Multi-Period DDR5 Decoding
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Solution Overview
Problem
Decoding errors in command address signals due to incorrect sampling of chip select signals in memory systems, particularly in DDR5 DRAM, where chip select signals remain active for multiple system sampling periods, leading to erroneous decoding of command address signals.
Innovation Solution
A chip select signal control circuit comprising a first and second control signal generation circuit, a chip select signal sampling circuit, and a logic control circuit, which utilize sampling of chip select and command address signals across multiple system sampling periods to ensure correct decoding by applying preset rules and logical checks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chip select signal sampling is performed using conventional single-period methods, then the circuit complexity is low, but decoding errors occur when chip select signals remain active for multiple system sampling periods
Solution Approach 1:
The patent performs preliminary sampling of the chip select signal in advance (in the previous system sampling period) before the actual command address signal decoding occurs. This preliminary sampled chip select signal is then used to control whether to sample the command address signal in the current period, preventing decoding errors by ensuring the chip select signal state is known beforehand.
Solution Approach 2:
The patent introduces an intermediate control signal (first control signal/second control signal) that mediates between the sampled chip select signal and the command address signal sampling. This intermediate signal acts as a gatekeeper, enabling or disabling the sampling of command address signals based on the chip select signal state, thereby preventing erroneous decoding without requiring complex direct comparison circuits.
2Reliability
If multiple sampling periods are used to ensure correct decoding, then decoding accuracy improves, but the circuit complexity and processing time increase
Solution Approach 1:
The chip select signal is sampled in advance in the previous system sampling period, so that by the time command address signal decoding is needed, the chip select signal state is already captured and stored. This eliminates the need to wait for additional sampling periods, maintaining fast processing while ensuring accurate decoding.
Solution Approach 2:
The patent divides the control into two separate control signal generation circuits: one for even clock cycles and one for odd clock cycles. Each circuit handles sampling for its specific clock phase, allowing parallel processing and eliminating the need for sequential multi-period sampling, thus reducing processing time while maintaining accuracy.
3Productivity
If conventional sampling methods are used, then the processing speed is high, but decoding errors occur due to incorrect chip select signal sampling
Solution Approach 1:
The patent employs periodic sampling synchronized with the system clock, using separate control signal generation circuits for even and odd clock cycles. This periodic sampling approach ensures that the chip select signal is captured at the correct timing intervals, maintaining high processing speed while preventing decoding errors through proper synchronization.
Solution Approach 2:
The patent uses the previously sampled chip select signal as feedback to control the sampling of the command address signal. The logic control circuit receives the sampled chip select signal and uses it to generate control signals that enable or disable command address signal sampling, creating a feedback mechanism that ensures accurate decoding without sacrificing processing speed.
Data Source
AI summary
Embodiments of the present disclosure disclose a chip select signal control circuit. The chip select signal control circuit includes: a first control signal generation circuit, a second control signal generation circuit, a chip select signal sampling circuit, and a logic control circuit. The first control signal generation circuit outputs a first control signal according to a first chip select sampling signal and a first command address sampling signal obtained in the previous two system sampling periods. The second control signal generation circuit outputs a second control signal according to a second chip select sampling signal and a second command address sampling signal obtained in the previous system sampling period. The logic control circuit controls the output of a current chip select sampling signal according to the first control signal and the second control signal.