10.4.12.4 Dual Port RAM for IGLOO®, ProASIC® 3 and Fusion Implementation Rules

Caveats for Dual Port RAM generation

Consider the following caveats when generating Dual Port RAM:
  • If a word width of 9 is used for Read, then Write configurations of 1, 2 or 4 cause the MSB of the output to be undefined. These configurations are not supported. However, configurations that do not use the 9th bit (For example, a Read width of 512x8 and a Write width of 1024x4) are supported.
  • The core configurator only supports depth and width RAM cascading up to 64 blocks.
  • The core configurator software does not generate RAM based on a specific device. It is your responsibility to make sure the RAM fits physically on the device. Dynamic configuration of the aspect ratios is supported only in the Fusion RAM with Initialization core.
  • The software returns a configuration error for unsupported configurations.

Tips

Use the following tips when generating Dual Port RAM:
  • Writing different data to the same address using both ports in Dual Port RAM is undefined and should be avoided.
  • All unused inputs must be grounded.
  • WMODE is ignored during read operation.
  • RESET does not reset the memory contents. It resets only the output.
  • Writing to and reading from the same address is undefined and should be avoided. When using the RAM4K9 in Two Port mode, care should be taken that Read and Write operations are not going on simultaneously, by properly driving the WEN and BLK signals. This becomes extremely important in cases where multiple RAM blocks are cascaded for deeper memories. In such case, BLK must be used for address decoding.