Description

Keyword: RAM18, RAMB36, FIFO

The INIT values of my RAM18 are all set to zero when it is packed together with a FIFO in a RAMB36 Component.

When I lock the memories to separate locations, the INIT values of the BRAM get assigned correctly. Why does this occur?

Solution

This is a Map packing bug where the INIT values of a BRAM get corrupted when packed in the same RAM component as the FIFO. This issue will be fixed in ISE version 10.1 SP2.

Meanwhile, the problem can be avoided by locking the BRAM and FIFO instances to different sites, or by using any packing constraint that prevents the BRAM and FIFO from being packed together.