Data is written synchronously into the RAM for both types. The primary difference between distributed RAM and dedicated block RAM lies in the way data is read from the RAM. See the following table.
| Action | Distributed RAM | Dedicated Block RAM |
|---|---|---|
| Write | Synchronous | Synchronous |
| Read | Asynchronous | Synchronous |
Whether to use distributed RAM or dedicated block RAM can depend upon the characteristics of the RAM described in the HDL source code, the availability of block RAM resources, and whether you have forced a specific implementation style using RAM_STYLE attribute.