Final answer:
The gate descriptions that are not standard and could potentially be invalid are Asymmetric Inverter and Dynamic Footed asymmetric NOR. Pseudo-NMOS dynamic NOR is invalid due to the contradiction between pseudo-NMOS and dynamic logic methodologies.
Step-by-step explanation:
To determine which of the listed gate descriptions are not valid, we need to understand each term within the context of digital circuit design. Typically, gate descriptions involve a combination of logical functions and design styles that are well-known in electronics engineering.
- Asymmetric Inverter: This is a somewhat unconventional term, as inverters are usually symmetric in the sense that they provide the same level of drive strength for both the logical high and low outputs. However, the concept of having an asymmetric drive strength is plausible in certain design scenarios where the pull-up and pull-down networks are intentionally unbalanced.
- Hi-Skewed Asymmetric NAND: This term suggests that the NAND gate is designed with a high skew towards one logical output over the other. It is theoretically possible to design a NAND gate that is skewed, though it's not a standard industry term.
- Pseudo-NMOS AOI221: This term combines a pseudo-NMOS logic design style with a complex gate that performs an AND-OR-INVERT operation with two inputs of 2, one input of 1, and one output. Pseudo-NMOS is a valid approach to gate design, particularly in low-power applications, so this one seems potentially valid.
- Pseudo-NMOS dynamic NOR: Pseudo-NMOS refers to a static logic design style, while dynamic logic is a different approach that uses precharge and evaluate phases in its operation. Therefore, the combination of pseudo-NMOS with dynamic logic in the context of a NOR gate description appears to be contradictory.
- Dynamic Footed asymmetric NOR: Dynamic logic gates can indeed be footed, referring to a design technique that adds a transistor to mitigate leakage during the precharge phase. However, coupling this with 'asymmetric' is unusual and not a standard term in digital design, which casts doubt on its validity.
- Dynamic NAND with keeper: This is a valid design that combines a dynamic NAND gate with a keeper transistor to maintain the state of the dynamic node during the hold phase, which is common in high-performance circuits.
Based on these considerations, the descriptions that are not standard and could potentially be invalid are Asymmetric Inverter and Dynamic Footed asymmetric NOR. The term Pseudo-NMOS dynamic NOR seems to be invalid due to the contradictory nature of static pseudo-NMOS and dynamic logic. The rest of the terms are either valid or could potentially be valid in certain specialized applications.