7986310fa0
FPGAs support different widths for the read and write port of the block SRAM cells. The DMAC can make use of this feature when the source and destination interface have a different width to up-size/down-size the data bus. Using memory cells with asymmetric port width consumes the same amount of SRAM cells, but allows to bypass the re-size blocks inside the DMAC that are otherwise used for up- and down-sizing. This reduces overall resource usage and can improve timing. If the ratio between the destination and source port is too larger to be handled by SRAM alone the SRAM block will be configured to do partial up- or down-sizing and a resize block will be inserted to take care of the remaining up-/down-sizing. E.g. if a 256-bit interface is connected to a 32-bit interface the SRAM will be used to do an initial resizing of 256 bit to 64 bit and a resize block will be used to do the remaining resizing from 64 bit to 32 bit. Currently this feature is disabled for Intel FPGAs since Quartus does not properly infer a block RAM with different read and write port widths from the current ad_asym_mem module. Once that has been resolved support for asymmetric memories can also be enabled in the DMAC. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> |
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