Description

When the RAM_STYLE attribute is specified in capital letters in RTL, Vivado Synthesis still infers a distributed RAM.

Solution

This issue was noted in -1 speed grade devices. 

Both RAM_STYLE=BLOCK and ram_style=block work with -2 speed grade devices.

However setting RAM_STYLE=BLOCK does not infer a block RAM in -1 speed grade devices, but instead infers a distributed RAM. 

Setting the ram style to block in lower case letters (ram_style = block) does infer a block RAM for -1 speed grade devices.

The issue is fixed in the 2013.2 release.

For prior versions, the workaround is to always specify the attribute in lower case (ram_style = block).

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