Command Decoder State-Dependent Logic for Memory Systems
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Solution Overview
Problem
Conventional memory systems face limitations in increasing the number of commands that can be decoded due to the binary nature of command signals, leading to a maximum of eight possible commands, which is insufficient for future needs, and adding more command signals requires additional external terminals, increasing the physical size and complexity of memory devices.
Innovation Solution
A command decoder that generates internal control signals based on the latched logic levels of command signals in combination with the operating state of the memory system, allowing for the same number of commands with fewer signal lines or increasing commands without additional external terminals by using the bank active state and other signals like A10.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If more command signals are added to increase the number of decodable commands, then the number of commands increases, but the number of external terminals increases
Solution Approach 1:
The patent merges the command decoding function with the operating state machine. The command decoder now receives both command signals and operating state information (from mode registers and state flags) to determine the actual command to execute. This combination allows the system to differentiate between multiple commands using the same signal patterns, effectively increasing command capacity without adding external terminals.
Solution Approach 2:
The patent introduces mode registers and state flags as intermediary elements between the command signals and the execution logic. These intermediaries store operating state information that modifies the interpretation of command signals. For example, a given signal pattern may be interpreted as different commands depending on the current mode register values, allowing one set of terminals to control multiple commands through state-dependent decoding.
2Adaptability or versatility
If the number of command signals is increased, then more commands can be decoded, but the physical size of the memory device increases
Solution Approach 1:
The patent makes the existing command signals and terminals universal by enabling them to represent multiple different commands depending on the operating state. The same physical terminal and signal pattern can serve multiple command functions by combining signal interpretation with state machine context. This multi-functionality allows the memory device to support more commands without increasing the number of physical terminals or device area.
3Adaptability or versatility
If additional command signals are added, then command versatility increases, but PCB complexity increases
Solution Approach 1:
The patent implements feedback mechanisms where the operating state (stored in mode registers and state flags) feeds back into the command decoding process. The decoder continuously monitors the current state and uses this feedback to correctly interpret incoming command signals. This feedback loop allows the system to maintain command versatility without adding external signal lines, as the state information is already available within the device through existing control and data buses.
Data Source
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AI summary
A system and method for decoding command signals that includes a command decoder configured to generate internal control signals to perform an operation based on the command signals and an operating state. The same combination of command signals can request different commands depending on the operating state. A command is selected from a first set of operations according to the command signals when the memory system is in a first operating state and a command is selected from a second set of operations according to the command signals when the memory system is in a second operating state.