Clearing Bitstreams - 2023.2 English

Vivado Design Suite User Guide: Dynamic Function eXchange (UG909)

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2023.2 English

Unlike the bitstream types noted above, this type is for UltraScale devices only (UltraScale+ does not have this requirement). A new requirement for this architecture is to clear an existing module before loading a new module. This clearing bitstream prepares the device for the delivery of any subsequent partial bitstream for that RP by establishing the global signal mask for the region to be reconfigured. Although the existing module is technically not removed (the current logical module remains), it is easiest to think of it this way. If a clearing bitstream is not delivered, the subsequent RM will not be initialized.

Clearing bitstreams are not partial bitstreams. They comprise less than 10% of the frames for the target region and are therefore less than 10% the size of the corresponding partial bitstreams. They do not change the functionality but shut down clocks driving logic in the region. They must be delivered between partial bitstreams and should always be followed as soon as possible by the next partial bitstream.

Each clearing bitstream is built for a specific RM and must be applied after that module has been used, and must be sent to the configuration engine immediately before the next partial bitstream is delivered. For example, to transition from module A to module B, the clearing bitstream for A must be delivered just before the partial bitstream for B is delivered. To transition from module B back to module A, the clearing bitstream for B must be delivered just before the partial bitstream for A is delivered. This is the case even if any partial bitstream in question is a blanking bitstream.

Clearing bitstreams are automatically generated and have the same name as partial bitstreams with _clear at the end. Looking at the example above, if top_first is an UltraScale device design, the clearing bit file name would be top_first_pblock_red_partial_clear.bit.