How Do Wrapper Chains and Wrapper Cells Work in Detail?

原创已于 2024-07-16 11:16:05 修改 · 393 阅读

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于 2021-12-28 20:29:40 首次发布

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Description

Question:

I am using the core wrapper feature of the DFTMAX tool. The user guide describes wrapper chain behavior from a high level, but it does not show detailed wrapper chain timing diagrams or logic schematics. In detail, how do wrapper chains and wrapper cells work?

Answer:

The following sections provide detailed timing and logic-value reference information for wrapper chain and wrapper cell behavior:

The examples show a mix of shared and dedicated wrapper cells. The simple wrapper flow examples use a single wrapper chain, and the maximized reuse examples use separate input and output wrapper chains. Although safe values are optional, all wrapper cells show safe values for completeness. If safe values are not used, you can "reconstruct" the cell by simply removing the safe value mux and its control and data signals, and pass the "0" leg of the mux on to the cfo pin of the cell.

In the maximized reuse flow, input wrapper chains are held in scan shift during inward-facing modes, and output wrapper chains are held in scan shift during outward-facing modes. During transition-delay ATPG, these wrapper chains generate transitions by shifting the opposite value into a wrapper cell from the preceding wrapper cell.

For more information about core wrapping and wrapper test modes, see the "Core Wrapping Concepts" section in the "Wrapping Cores" section of the DFT Design-for-Test User Guide.